diff --git a/modules/geoedgeRtdProvider.js b/modules/geoedgeRtdProvider.js
index fdd7aa2f5eb..646d2f4e786 100644
--- a/modules/geoedgeRtdProvider.js
+++ b/modules/geoedgeRtdProvider.js
@@ -258,8 +258,4 @@ export const geoedgeSubmodule = {
   onBidResponseEvent: conditionallyWrap
 };
 
-export function beforeInit() {
-  submodule('realTimeData', geoedgeSubmodule);
-}
-
-beforeInit();
+submodule('realTimeData', geoedgeSubmodule);
diff --git a/modules/prebidServerBidAdapter/index.js b/modules/prebidServerBidAdapter/index.js
index 3cc38923d57..3cae4497354 100644
--- a/modules/prebidServerBidAdapter/index.js
+++ b/modules/prebidServerBidAdapter/index.js
@@ -18,7 +18,7 @@ import {
   deepAccess,
 } from '../../src/utils.js';
 import CONSTANTS from '../../src/constants.json';
-import adapterManager from '../../src/adapterManager.js';
+import adapterManager, {s2sActivityParams} from '../../src/adapterManager.js';
 import {config} from '../../src/config.js';
 import {addComponentAuction, isValid} from '../../src/adapters/bidderFactory.js';
 import * as events from '../../src/events.js';
@@ -29,6 +29,8 @@ import {hook} from '../../src/hook.js';
 import {hasPurpose1Consent} from '../../src/utils/gpdr.js';
 import {buildPBSRequest, interpretPBSResponse} from './ortbConverter.js';
 import {useMetrics} from '../../src/utils/perfMetrics.js';
+import {isActivityAllowed} from '../../src/activities/rules.js';
+import {ACTIVITY_TRANSMIT_UFPD} from '../../src/activities/activities.js';
 
 const getConfig = config.getConfig;
 
@@ -571,7 +573,11 @@ export const processPBSRequest = hook('sync', function (s2sBidRequest, bidReques
         }
       },
       requestJson,
-      {contentType: 'text/plain', withCredentials: true}
+      {
+        contentType: 'text/plain',
+        withCredentials: true,
+        browsingTopics: isActivityAllowed(ACTIVITY_TRANSMIT_UFPD, s2sActivityParams(s2sBidRequest.s2sConfig))
+      }
     );
   } else {
     logError('PBS request not made.  Check endpoints.');
diff --git a/src/adapters/bidderFactory.js b/src/adapters/bidderFactory.js
index d316ad5924c..b31019a6d79 100644
--- a/src/adapters/bidderFactory.js
+++ b/src/adapters/bidderFactory.js
@@ -25,7 +25,7 @@ import {useMetrics} from '../utils/perfMetrics.js';
 import {isActivityAllowed} from '../activities/rules.js';
 import {activityParams} from '../activities/activityParams.js';
 import {MODULE_TYPE_BIDDER} from '../activities/modules.js';
-import {ACTIVITY_TRANSMIT_TID} from '../activities/activities.js';
+import {ACTIVITY_TRANSMIT_TID, ACTIVITY_TRANSMIT_UFPD} from '../activities/activities.js';
 
 /**
  * This file aims to support Adapters during the Prebid 0.x -> 1.x transition.
@@ -454,6 +454,15 @@ export const processBidderRequests = hook('sync', function (spec, bids, bidderRe
     onRequest(request);
 
     const networkDone = requestMetrics.startTiming('net');
+
+    function getOptions(defaults) {
+      const ro = request.options;
+      return Object.assign(defaults, ro, {
+        browsingTopics: ro?.hasOwnProperty('browsingTopics') && !ro.browsingTopics
+          ? false
+          : isActivityAllowed(ACTIVITY_TRANSMIT_UFPD, activityParams(MODULE_TYPE_BIDDER, spec.code))
+      })
+    }
     switch (request.method) {
       case 'GET':
         ajax(
@@ -463,10 +472,10 @@ export const processBidderRequests = hook('sync', function (spec, bids, bidderRe
             error: onFailure
           },
           undefined,
-          Object.assign({
+          getOptions({
             method: 'GET',
             withCredentials: true
-          }, request.options)
+          })
         );
         break;
       case 'POST':
@@ -477,11 +486,11 @@ export const processBidderRequests = hook('sync', function (spec, bids, bidderRe
             error: onFailure
           },
           typeof request.data === 'string' ? request.data : JSON.stringify(request.data),
-          Object.assign({
+          getOptions({
             method: 'POST',
             contentType: 'text/plain',
             withCredentials: true
-          }, request.options)
+          })
         );
         break;
       default:
diff --git a/src/ajax.js b/src/ajax.js
index 5e926f3210d..0601cc0e22b 100644
--- a/src/ajax.js
+++ b/src/ajax.js
@@ -1,99 +1,138 @@
-import { config } from './config.js';
-import { logMessage, logError, parseUrl, buildUrl, _each } from './utils.js';
+import {config} from './config.js';
+import {buildUrl, logError, parseUrl} from './utils.js';
 
-const XHR_DONE = 4;
+export const dep = {
+  fetch: window.fetch.bind(window),
+  makeRequest: (r, o) => new Request(r, o),
+  timeout(timeout, resource) {
+    const ctl = new AbortController();
+    let cancelTimer = setTimeout(() => {
+      ctl.abort();
+      logError(`Request timeout after ${timeout}ms`, resource);
+      cancelTimer = null;
+    }, timeout);
+    return {
+      signal: ctl.signal,
+      done() {
+        cancelTimer && clearTimeout(cancelTimer)
+      }
+    }
+  }
+}
+
+const GET = 'GET';
+const POST = 'POST';
+const CTYPE = 'Content-Type';
 
 /**
- * Simple IE9+ and cross-browser ajax request function
- * Note: x-domain requests in IE9 do not support the use of cookies
- *
- * @param url string url
- * @param callback {object | function} callback
- * @param data mixed data
- * @param options object
+ * transform legacy `ajax` parameters into a fetch request.
+ * @returns {Request}
  */
-export const ajax = ajaxBuilder();
-
-export function ajaxBuilder(timeout = 3000, {request, done} = {}) {
-  return function(url, callback, data, options = {}) {
-    try {
-      let x;
-      let method = options.method || (data ? 'POST' : 'GET');
-      let parser = document.createElement('a');
-      parser.href = url;
-
-      let callbacks = typeof callback === 'object' && callback !== null ? callback : {
-        success: function() {
-          logMessage('xhr success');
-        },
-        error: function(e) {
-          logError('xhr error', null, e);
-        }
-      };
+export function toFetchRequest(url, data, options = {}) {
+  const method = options.method || (data ? POST : GET);
+  if (method === GET && data) {
+    const urlInfo = parseUrl(url, options);
+    Object.assign(urlInfo.search, data);
+    url = buildUrl(urlInfo);
+  }
+  const headers = new Headers(options.customHeaders);
+  headers.set(CTYPE, options.contentType || 'text/plain');
+  const rqOpts = {
+    method,
+    headers
+  }
+  if (method !== GET && data) {
+    rqOpts.body = data;
+  }
+  if (options.withCredentials) {
+    rqOpts.credentials = 'include';
+  }
+  if (options.browsingTopics && isSecureContext) {
+    // the Request constructor will throw an exception if the browser supports topics
+    // but we're not in a secure context
+    rqOpts.browsingTopics = true;
+  }
+  return dep.makeRequest(url, rqOpts);
+}
 
-      if (typeof callback === 'function') {
-        callbacks.success = callback;
-      }
+/**
+ * Return a version of `fetch` that automatically cancels requests after `timeout` milliseconds.
+ *
+ * If provided, `request` and `done` should be functions accepting a single argument.
+ * `request` is invoked at the beginning of each request, and `done` at the end; both are passed its origin.
+ *
+ * @returns {function(*, {}?): Promise<Response>}
+ */
+export function fetcherFactory(timeout = 3000, {request, done} = {}) {
+  let fetcher = (resource, options) => {
+    let to;
+    if (timeout != null && options?.signal == null && !config.getConfig('disableAjaxTimeout')) {
+      to = dep.timeout(timeout, resource);
+      options = Object.assign({signal: to.signal}, options);
+    }
+    let pm = dep.fetch(resource, options);
+    if (to?.done != null) pm = pm.finally(to.done);
+    return pm;
+  };
 
-      x = new window.XMLHttpRequest();
+  if (request != null || done != null) {
+    fetcher = ((fetch) => function (resource, options) {
+      const origin = new URL(resource?.url == null ? resource : resource.url, document.location).origin;
+      let req = fetch(resource, options);
+      request && request(origin);
+      if (done) req = req.finally(() => done(origin));
+      return req;
+    })(fetcher);
+  }
+  return fetcher;
+}
 
-      x.onreadystatechange = function () {
-        if (x.readyState === XHR_DONE) {
-          if (typeof done === 'function') {
-            done(parser.origin);
-          }
-          let status = x.status;
-          if ((status >= 200 && status < 300) || status === 304) {
-            callbacks.success(x.responseText, x);
-          } else {
-            callbacks.error(x.statusText, x);
-          }
+function toXHR({status, statusText = '', headers, url}, responseText) {
+  let xml = 0;
+  return {
+    readyState: XMLHttpRequest.DONE,
+    status,
+    statusText,
+    responseText,
+    response: responseText,
+    responseType: '',
+    responseURL: url,
+    get responseXML() {
+      if (xml === 0) {
+        try {
+          xml = new DOMParser().parseFromString(responseText, headers?.get(CTYPE)?.split(';')?.[0])
+        } catch (e) {
+          xml = null;
+          logError(e);
         }
-      };
-
-      // Disabled timeout temporarily to avoid xhr failed requests. https://github.com/prebid/Prebid.js/issues/2648
-      if (!config.getConfig('disableAjaxTimeout')) {
-        x.ontimeout = function () {
-          logError('  xhr timeout after ', x.timeout, 'ms');
-        };
       }
+      return xml;
+    },
+    getResponseHeader: (header) => headers?.has(header) ? headers.get(header) : null,
+  }
+}
 
-      if (method === 'GET' && data) {
-        let urlInfo = parseUrl(url, options);
-        Object.assign(urlInfo.search, data);
-        url = buildUrl(urlInfo);
-      }
-
-      x.open(method, url, true);
-      // IE needs timeout to be set after open - see #1410
-      // Disabled timeout temporarily to avoid xhr failed requests. https://github.com/prebid/Prebid.js/issues/2648
-      if (!config.getConfig('disableAjaxTimeout')) {
-        x.timeout = timeout;
-      }
-
-      if (options.withCredentials) {
-        x.withCredentials = true;
-      }
-      _each(options.customHeaders, (value, header) => {
-        x.setRequestHeader(header, value);
-      });
-      if (options.preflight) {
-        x.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
-      }
-      x.setRequestHeader('Content-Type', options.contentType || 'text/plain');
-
-      if (typeof request === 'function') {
-        request(parser.origin);
-      }
+/**
+ * attach legacy `ajax` callbacks to a fetch promise.
+ */
+export function attachCallbacks(fetchPm, callback) {
+  const {success, error} = typeof callback === 'object' && callback != null ? callback : {
+    success: typeof callback === 'function' ? callback : () => null,
+    error: (e, x) => logError('Network error', e, x)
+  };
+  fetchPm.then(response => response.text().then((responseText) => [response, responseText]))
+    .then(([response, responseText]) => {
+      const xhr = toXHR(response, responseText);
+      response.ok || response.status === 304 ? success(responseText, xhr) : error(response.statusText, xhr);
+    }, () => error('', toXHR({status: 0}, '')));
+}
 
-      if (method === 'POST' && data) {
-        x.send(data);
-      } else {
-        x.send();
-      }
-    } catch (error) {
-      logError('xhr construction', error);
-      typeof callback === 'object' && callback !== null && callback.error(error);
-    }
-  }
+export function ajaxBuilder(timeout = 3000, {request, done} = {}) {
+  const fetcher = fetcherFactory(timeout, {request, done});
+  return function (url, callback, data, options = {}) {
+    attachCallbacks(fetcher(toFetchRequest(url, data, options)), callback);
+  };
 }
+
+export const ajax = ajaxBuilder();
+export const fetch = fetcherFactory();
diff --git a/test/mocks/xhr.js b/test/mocks/xhr.js
index 424100f870c..e7b1d96f0a4 100644
--- a/test/mocks/xhr.js
+++ b/test/mocks/xhr.js
@@ -1,12 +1,236 @@
 import {getUniqueIdentifierStr} from '../../src/utils.js';
+import {GreedyPromise} from '../../src/utils/promise.js';
+import {fakeXhr} from 'nise';
+import {dep} from 'src/ajax.js';
 
-export let server = sinon.createFakeServer();
-export let xhr = global.XMLHttpRequest;
+export const xhr = sinon.useFakeXMLHttpRequest();
+export const server = mockFetchServer();
 
-beforeEach(function() {
-  server.restore();
-  server = sinon.createFakeServer();
-  xhr = global.XMLHttpRequest;
+/**
+ * An (incomplete) replica of nise's fakeServer, but backing fetch used in ajax.js (rather than XHR).
+ */
+function mockFetchServer() {
+  const sandbox = sinon.createSandbox();
+  const bodies = new WeakMap();
+  const requests = [];
+  const {DONE, UNSENT} = XMLHttpRequest;
+
+  function makeRequest(resource, options) {
+    const requestBody = options?.body || bodies.get(resource);
+    const request = new Request(resource, options);
+    bodies.set(request, requestBody);
+    return request;
+  }
+
+  function mockXHR(resource, options) {
+    let resolve, reject;
+    const promise = new GreedyPromise((res, rej) => {
+      resolve = res;
+      reject = rej;
+    });
+
+    function error(reason = new TypeError('Failed to fetch')) {
+      mockReq.status = 0;
+      reject(reason);
+    }
+
+    const request = makeRequest(resource, options);
+    request.signal.onabort = () => error(new DOMException('The user aborted a request'));
+    let responseHeaders;
+
+    const mockReq = {
+      fetch: {
+        request,
+        requestBody: bodies.get(request),
+        promise,
+      },
+      readyState: UNSENT,
+      url: request.url,
+      method: request.method,
+      requestBody: bodies.get(request),
+      status: 0,
+      statusText: '',
+      requestHeaders: new Proxy(request.headers, {
+        get(target, prop) {
+          return typeof prop === 'string' && target.has(prop) ? target.get(prop) : {}[prop];
+        },
+        has(target, prop) {
+          return typeof prop === 'string' && target.has(prop);
+        },
+        ownKeys(target) {
+          return Array.from(target.keys());
+        },
+        getOwnPropertyDescriptor(target, prop) {
+          if (typeof prop === 'string' && target.has(prop)) {
+            return {
+              enumerable: true,
+              configurable: true,
+              writable: false,
+              value: target.get(prop)
+            }
+          }
+        }
+      }),
+      withCredentials: request.credentials === 'include',
+      setStatus(status) {
+        // nise replaces invalid status with 200
+        status = typeof status === 'number' ? status : 200;
+        mockReq.status = status;
+        mockReq.statusText = fakeXhr.FakeXMLHttpRequest.statusCodes[status] || '';
+      },
+      setResponseHeaders(headers) {
+        responseHeaders = headers;
+      },
+      setResponseBody(body) {
+        if (mockReq.status === 0) {
+          error();
+          return;
+        }
+        const resp = Object.defineProperties(new Response(body, {
+          status: mockReq.status,
+          statusText: mockReq.statusText,
+          headers: responseHeaders || {},
+        }), {
+          url: {
+            get: () => mockReq.fetch.request.url,
+          }
+        });
+        mockReq.readyState = DONE;
+        // tests expect respond() to run everything immediately,
+        // so make body available syncronously
+        resp.text = () => GreedyPromise.resolve(body || '');
+        Object.assign(mockReq.fetch, {
+          response: resp,
+          responseBody: body || ''
+        })
+        resolve(resp);
+      },
+      respond(status = 200, headers, body) {
+        mockReq.setStatus(status);
+        mockReq.setResponseHeaders(headers);
+        mockReq.setResponseBody(body);
+      },
+      error
+    };
+    return mockReq;
+  }
+
+  let enabled = false;
+  let timeoutsEnabled = false;
+
+  function enable() {
+    if (!enabled) {
+      sandbox.stub(dep, 'fetch').callsFake((resource, options) => {
+        const req = mockXHR(resource, options);
+        requests.push(req);
+        return req.fetch.promise;
+      });
+      sandbox.stub(dep, 'makeRequest').callsFake(makeRequest);
+      const timeout = dep.timeout;
+      sandbox.stub(dep, 'timeout').callsFake(function () {
+        if (timeoutsEnabled) {
+          return timeout.apply(null, arguments);
+        } else {
+          return {};
+        }
+      });
+      enabled = true;
+    }
+  }
+
+  enable();
+
+  const responders = [];
+
+  function respondWith() {
+    let response, urlMatcher, methodMatcher;
+    urlMatcher = methodMatcher = () => true;
+    switch (arguments.length) {
+      case 1:
+        ([response] = arguments);
+        break;
+      case 2:
+        ([urlMatcher, response] = arguments);
+        break;
+      case 3:
+        ([methodMatcher, urlMatcher, response] = arguments);
+        methodMatcher = ((toMatch) => (method) => method === toMatch)(methodMatcher);
+        break;
+      default:
+        throw new Error('Invalid respondWith invocation');
+    }
+    if (typeof urlMatcher.exec === 'function') {
+      urlMatcher = ((rx) => (url) => rx.exec(url)?.slice(1))(urlMatcher);
+    } else if (typeof urlMatcher === 'string') {
+      urlMatcher = ((toMatch) => (url) => url === toMatch)(urlMatcher);
+    }
+    responders.push((req) => {
+      if (req.readyState !== DONE && methodMatcher(req.method)) {
+        const arg = urlMatcher(req.url);
+        if (arg) {
+          if (typeof response === 'function') {
+            response(req, ...(Array.isArray(arg) ? arg : []));
+          } else if (typeof response === 'string') {
+            req.respond(200, null, response);
+          } else {
+            req.respond.apply(req, response);
+          }
+        }
+      }
+    });
+  }
+
+  function resetState() {
+    requests.length = 0;
+    responders.length = 0;
+    timeoutsEnabled = false;
+  }
+
+  return {
+    requests,
+    enable,
+    restore() {
+      resetState();
+      sandbox.restore();
+      enabled = false;
+    },
+    reset() {
+      sandbox.resetHistory();
+      resetState();
+    },
+    respondWith,
+    respond() {
+      if (arguments.length > 0) {
+        respondWith.apply(null, arguments);
+      }
+      requests.forEach(req => {
+        for (let i = responders.length - 1; i >= 0; i--) {
+          responders[i](req);
+          if (req.readyState === DONE) break;
+        }
+        if (req.readyState !== DONE) {
+          req.respond(404, {}, '');
+        }
+      });
+    },
+    /**
+     * the timeout mechanism is quite different between XHR and fetch
+     * by default, mocked fetch does not time out - to reflect fakeServer XHRs
+     * note that many tests will fire requests without caring or waiting for their response -
+     * if they are timed out later, during unrelated tests, the log messages might interfere with their
+     * assertions
+     */
+    get autoTimeout() {
+      return timeoutsEnabled;
+    },
+    set autoTimeout(val) {
+      timeoutsEnabled = !!val;
+    }
+  };
+}
+
+beforeEach(function () {
+  server.reset();
 });
 
 const bid = getUniqueIdentifierStr().substring(4);
@@ -20,12 +244,35 @@ afterEach(function () {
       return (s) => s.split('\n').map(s => `${preamble} ${s}`).join('\n');
     })();
 
+    function format(obj, body = null) {
+      if (obj == null) return obj;
+      const fmt = {};
+      let node = obj;
+      while (node != null) {
+        Object.keys(node).forEach((k) => {
+          const val = obj[k];
+          if (typeof val !== 'function' && !fmt.hasOwnProperty(k)) {
+            fmt[k] = val;
+          }
+        });
+        node = Object.getPrototypeOf(node);
+      }
+      if (obj.headers != null) {
+        fmt.headers = Object.fromEntries(obj.headers.entries())
+      }
+      fmt.body = body;
+      return fmt;
+    }
+
 
-    console.log(prepend(`XHR mock state after failure (for test '${this.currentTest.fullTitle()}'): ${server.requests.length} requests`))
+    console.log(prepend(`XHR mock state after failure (for test '${this.currentTest.fullTitle()}'): ${server.requests.length} requests`));
     server.requests.forEach((req, i) => {
       console.log(prepend(`Request #${i}:`));
-      console.log(prepend(JSON.stringify(req, null, 2)));
-    })
+      console.log(prepend(JSON.stringify({
+        request: format(req.fetch.request, req.fetch.requestBody),
+        response: format(req.fetch.response, req.fetch.responseBody)
+      }, null, 2)));
+    });
   }
 });
 /* eslint-enable */
diff --git a/test/spec/modules/adlooxAdServerVideo_spec.js b/test/spec/modules/adlooxAdServerVideo_spec.js
index a071c6bbe3f..58277bc830d 100644
--- a/test/spec/modules/adlooxAdServerVideo_spec.js
+++ b/test/spec/modules/adlooxAdServerVideo_spec.js
@@ -1,11 +1,11 @@
 import adapterManager from 'src/adapterManager.js';
 import analyticsAdapter from 'modules/adlooxAnalyticsAdapter.js';
-import { ajax } from 'src/ajax.js';
 import { buildVideoUrl } from 'modules/adlooxAdServerVideo.js';
 import { expect } from 'chai';
 import * as events from 'src/events.js';
 import { targeting } from 'src/targeting.js';
 import * as utils from 'src/utils.js';
+import {server} from '../../mocks/xhr.js';
 
 const analyticsAdapterName = 'adloox';
 
@@ -199,11 +199,9 @@ describe('Adloox Ad Server Video', function () {
     });
 
     describe('process VAST', function () {
-      let server = null;
       let BID = null;
       let getWinningBidsStub;
       beforeEach(function () {
-        server = sinon.createFakeServer();
         BID = utils.deepClone(bid);
         getWinningBidsStub = sinon.stub(targeting, 'getWinningBids')
         getWinningBidsStub.withArgs(adUnit.code).returns([ BID ]);
@@ -212,8 +210,6 @@ describe('Adloox Ad Server Video', function () {
         getWinningBidsStub.restore();
         getWinningBidsStub = undefined;
         BID = null;
-        server.restore();
-        server = null;
       });
 
       it('should return URL unchanged for non-VAST', function (done) {
diff --git a/test/spec/modules/adlooxRtdProvider_spec.js b/test/spec/modules/adlooxRtdProvider_spec.js
index 5b99789981f..0e26ef1afdb 100644
--- a/test/spec/modules/adlooxRtdProvider_spec.js
+++ b/test/spec/modules/adlooxRtdProvider_spec.js
@@ -1,12 +1,12 @@
 import adapterManager from 'src/adapterManager.js';
 import analyticsAdapter from 'modules/adlooxAnalyticsAdapter.js';
 import {auctionManager} from 'src/auctionManager.js';
-import { config as _config } from 'src/config.js';
 import { expect } from 'chai';
 import * as events from 'src/events.js';
 import * as prebidGlobal from 'src/prebidGlobal.js';
 import { subModuleObj as rtdProvider } from 'modules/adlooxRtdProvider.js';
 import * as utils from 'src/utils.js';
+import {server} from '../../mocks/xhr.js';
 
 const analyticsAdapterName = 'adloox';
 
@@ -139,16 +139,12 @@ describe('Adloox RTD Provider', function () {
       expect(analyticsAdapter.context).is.null;
     });
 
-    let server = null;
     let CONFIG = null;
     beforeEach(function () {
-      server = sinon.createFakeServer();
       CONFIG = utils.deepClone(config);
     });
     afterEach(function () {
       CONFIG = null;
-      server.restore();
-      server = null;
     });
 
     it('should fetch segments', function (done) {
diff --git a/test/spec/modules/categoryTranslation_spec.js b/test/spec/modules/categoryTranslation_spec.js
index 2301d6aab1b..d4f6aa66c7d 100644
--- a/test/spec/modules/categoryTranslation_spec.js
+++ b/test/spec/modules/categoryTranslation_spec.js
@@ -2,18 +2,16 @@ import { getAdserverCategoryHook, initTranslation, storage } from 'modules/categ
 import { config } from 'src/config.js';
 import * as utils from 'src/utils.js';
 import { expect } from 'chai';
+import {server} from '../../mocks/xhr.js';
 
 describe('category translation', function () {
-  let fakeTranslationServer;
   let getLocalStorageStub;
 
   beforeEach(function () {
-    fakeTranslationServer = sinon.fakeServer.create();
     getLocalStorageStub = sinon.stub(storage, 'getDataFromLocalStorage');
   });
 
   afterEach(function() {
-    fakeTranslationServer.reset();
     getLocalStorageStub.restore();
     config.resetConfig();
   });
@@ -73,7 +71,7 @@ describe('category translation', function () {
       }
     }));
     initTranslation();
-    expect(fakeTranslationServer.requests.length).to.equal(0);
+    expect(server.requests.length).to.equal(0);
     clock.restore();
   });
 
@@ -86,15 +84,15 @@ describe('category translation', function () {
       }
     }));
     initTranslation();
-    expect(fakeTranslationServer.requests.length).to.equal(1);
+    expect(server.requests.length).to.equal(1);
     clock.restore();
   });
 
   it('should use default mapping file if publisher has not defined in config', function () {
     getLocalStorageStub.returns(null);
     initTranslation('http://sample.com', 'somekey');
-    expect(fakeTranslationServer.requests.length).to.equal(1);
-    expect(fakeTranslationServer.requests[0].url).to.equal('http://sample.com');
+    expect(server.requests.length).to.equal(1);
+    expect(server.requests[0].url).to.equal('http://sample.com/');
   });
 
   it('should use publisher defined mapping file', function () {
@@ -105,7 +103,7 @@ describe('category translation', function () {
     });
     getLocalStorageStub.returns(null);
     initTranslation('http://sample.com', 'somekey');
-    expect(fakeTranslationServer.requests.length).to.equal(2);
-    expect(fakeTranslationServer.requests[0].url).to.equal('http://sample.com');
+    expect(server.requests.length).to.equal(2);
+    expect(server.requests[0].url).to.equal('http://sample.com/');
   });
 });
diff --git a/test/spec/modules/conversantAnalyticsAdapter_spec.js b/test/spec/modules/conversantAnalyticsAdapter_spec.js
index ce134f7f6af..f425535ce73 100644
--- a/test/spec/modules/conversantAnalyticsAdapter_spec.js
+++ b/test/spec/modules/conversantAnalyticsAdapter_spec.js
@@ -3,6 +3,7 @@ import {expect} from 'chai';
 import {default as conversantAnalytics, CNVR_CONSTANTS, cnvrHelper} from 'modules/conversantAnalyticsAdapter';
 import * as utils from 'src/utils.js';
 import * as prebidGlobal from 'src/prebidGlobal';
+import {server} from '../../mocks/xhr.js';
 
 import constants from 'src/constants.json'
 
@@ -10,14 +11,13 @@ let events = require('src/events');
 
 describe('Conversant analytics adapter tests', function() {
   let sandbox; // sinon sandbox to make restoring all stubbed objects easier
-  let xhr; // xhr stub from sinon for capturing data sent via ajax
   let clock; // clock stub from sinon to mock our cache cleanup interval
   let logInfoStub;
 
   const PREBID_VERSION = '1.2';
   const SITE_ID = 108060;
 
-  let requests = [];
+  let requests;
   const DATESTAMP = Date.now();
 
   const VALID_CONFIGURATION = {
@@ -36,10 +36,9 @@ describe('Conversant analytics adapter tests', function() {
   };
 
   beforeEach(function () {
+    requests = server.requests;
     sandbox = sinon.sandbox.create();
     sandbox.stub(events, 'getEvents').returns([]); // need to stub this otherwise unwanted events seem to get fired during testing
-    xhr = sandbox.useFakeXMLHttpRequest(); // allows us to capture ajax requests
-    xhr.onCreate = function (req) { requests.push(req); }; // save ajax requests in a private array for testing purposes
     let getGlobalStub = {
       version: PREBID_VERSION,
       getUserIds: function() { // userIdTargeting.js init() gets called on AUCTION_END so we need to mock this function.
@@ -60,7 +59,6 @@ describe('Conversant analytics adapter tests', function() {
 
   afterEach(function () {
     sandbox.restore();
-    requests = []; // clean up any requests in our ajax request capture array.
     conversantAnalytics.disableAnalytics();
   });
 
diff --git a/test/spec/modules/currency_spec.js b/test/spec/modules/currency_spec.js
index 88c640e38cc..f7c2580f3f3 100644
--- a/test/spec/modules/currency_spec.js
+++ b/test/spec/modules/currency_spec.js
@@ -14,6 +14,7 @@ import {
 } from 'modules/currency.js';
 import {createBid} from '../../../src/bidfactory.js';
 import CONSTANTS from '../../../src/constants.json';
+import {server} from '../../mocks/xhr.js';
 
 var assert = require('chai').assert;
 var expect = require('chai').expect;
@@ -30,12 +31,11 @@ describe('currency', function () {
   }
 
   beforeEach(function () {
-    fakeCurrencyFileServer = sinon.fakeServer.create();
+    fakeCurrencyFileServer = server;
     ready.reset();
   });
 
   afterEach(function () {
-    fakeCurrencyFileServer.restore();
     setConfig({});
   });
 
diff --git a/test/spec/modules/dmdIdSystem_spec.js b/test/spec/modules/dmdIdSystem_spec.js
index 3096a8e55f5..16c32f184a3 100644
--- a/test/spec/modules/dmdIdSystem_spec.js
+++ b/test/spec/modules/dmdIdSystem_spec.js
@@ -60,7 +60,7 @@ describe('Dmd ID System', function () {
 
   it('Should invoke callback with response from API call', function () {
     const callbackSpy = sinon.spy();
-    const domain = utils.getWindowLocation()
+    const domain = utils.getWindowLocation().href;
     const callback = dmdIdSubmodule.getId(config).callback;
     callback(callbackSpy);
     const request = server.requests[0];
@@ -73,7 +73,7 @@ describe('Dmd ID System', function () {
 
   it('Should log error if API response is not valid', function () {
     const callbackSpy = sinon.spy();
-    const domain = utils.getWindowLocation()
+    const domain = utils.getWindowLocation().href;
     const callback = dmdIdSubmodule.getId(config).callback;
     callback(callbackSpy);
     const request = server.requests[0];
diff --git a/test/spec/modules/euidIdSystem_spec.js b/test/spec/modules/euidIdSystem_spec.js
index 9a016b0facd..4f6bacebe6a 100644
--- a/test/spec/modules/euidIdSystem_spec.js
+++ b/test/spec/modules/euidIdSystem_spec.js
@@ -1,13 +1,9 @@
-import {coreStorage, init, setSubmoduleRegistry, requestBidsHook} from 'modules/userId/index.js';
+import {coreStorage, init, setSubmoduleRegistry} from 'modules/userId/index.js';
 import {config} from 'src/config.js';
-import * as utils from 'src/utils.js';
-import { euidIdSubmodule } from 'modules/euidIdSystem.js';
+import {euidIdSubmodule} from 'modules/euidIdSystem.js';
 import 'modules/consentManagement.js';
 import 'src/prebid.js';
-import { getGlobal } from 'src/prebidGlobal.js';
-import { server } from 'test/mocks/xhr.js';
-import { configureTimerInterceptors } from 'test/mocks/timers.js';
-import { cookieHelpers, runAuction, apiHelpers, setGdprApplies } from './uid2IdSystem_helpers.js';
+import {apiHelpers, cookieHelpers, runAuction, setGdprApplies} from './uid2IdSystem_helpers.js';
 import {hook} from 'src/hook.js';
 import {uninstall as uninstallGdprEnforcement} from 'modules/gdprEnforcement.js';
 
@@ -32,12 +28,15 @@ const makePrebidConfig = (params = null, extraSettings = {}, debug = false) => (
 const apiUrl = 'https://prod.euid.eu/v2/token/refresh';
 const headers = { 'Content-Type': 'application/json' };
 const makeSuccessResponseBody = () => btoa(JSON.stringify({ status: 'success', body: { ...apiHelpers.makeTokenResponse(initialToken), advertising_token: refreshedToken } }));
-const configureEuidResponse = (httpStatus, response) => server.respondWith('POST', apiUrl, (xhr) => xhr.respond(httpStatus, headers, response));
 const expectToken = (bid, token) => expect(bid?.userId ?? {}).to.deep.include(makeEuidIdentityContainer(token));
 const expectNoIdentity = (bid) => expect(bid).to.not.haveOwnProperty('userId');
 
 describe('EUID module', function() {
   let suiteSandbox, testSandbox, timerSpy, fullTestTitle, restoreSubtleToUndefined = false;
+  let server;
+
+  const configureEuidResponse = (httpStatus, response) => server.respondWith('POST', apiUrl, (xhr) => xhr.respond(httpStatus, headers, response));
+
   before(function() {
     uninstallGdprEnforcement();
     hook.ready();
@@ -54,10 +53,12 @@ describe('EUID module', function() {
     if (restoreSubtleToUndefined) window.crypto.subtle = undefined;
   });
   beforeEach(function() {
+    server = sinon.createFakeServer();
     init(config);
     setSubmoduleRegistry([euidIdSubmodule]);
   });
   afterEach(function() {
+    server.restore();
     $$PREBID_GLOBAL$$.requestBids.removeAll();
     config.resetConfig();
     cookieHelpers.clearCookies(moduleCookieName, publisherCookieName);
@@ -116,7 +117,7 @@ describe('EUID module', function() {
     const euidToken = apiHelpers.makeTokenResponse(initialToken, true, true);
     configureEuidResponse(200, makeSuccessResponseBody());
     config.setConfig(makePrebidConfig({euidToken}));
-    apiHelpers.respondAfterDelay(1);
+    apiHelpers.respondAfterDelay(1, server);
     const bid = await runAuction();
     expectToken(bid, refreshedToken);
   });
diff --git a/test/spec/modules/feedadBidAdapter_spec.js b/test/spec/modules/feedadBidAdapter_spec.js
index 152adba9d00..cb81c6f06de 100644
--- a/test/spec/modules/feedadBidAdapter_spec.js
+++ b/test/spec/modules/feedadBidAdapter_spec.js
@@ -621,7 +621,7 @@ describe('FeedAdAdapter', function () {
           expect(call.url).to.equal('https://api.feedad.com/1/prebid/web/events');
           expect(JSON.parse(call.requestBody)).to.deep.equal(expectedData);
           expect(call.method).to.equal('POST');
-          expect(call.requestHeaders).to.include({'Content-Type': 'application/json;charset=utf-8'});
+          expect(call.requestHeaders).to.include({'Content-Type': 'application/json'});
         })
       });
     });
diff --git a/test/spec/modules/geoedgeRtdProvider_spec.js b/test/spec/modules/geoedgeRtdProvider_spec.js
index 2f2fc8e2775..96da2e3dbd7 100644
--- a/test/spec/modules/geoedgeRtdProvider_spec.js
+++ b/test/spec/modules/geoedgeRtdProvider_spec.js
@@ -1,8 +1,15 @@
 import * as utils from '../../../src/utils.js';
-import { loadExternalScript } from '../../../src/adloader.js';
-import * as hook from '../../../src/hook.js'
-import { beforeInit, geoedgeSubmodule, setWrapper, wrapper, htmlPlaceholder, WRAPPER_URL, getClientUrl, getInPageUrl } from '../../../modules/geoedgeRtdProvider.js';
-import { server } from '../../../test/mocks/xhr.js';
+import {loadExternalScript} from '../../../src/adloader.js';
+import {
+  geoedgeSubmodule,
+  getClientUrl,
+  getInPageUrl,
+  htmlPlaceholder,
+  setWrapper,
+  wrapper,
+  WRAPPER_URL
+} from '../../../modules/geoedgeRtdProvider.js';
+import {server} from '../../../test/mocks/xhr.js';
 import * as events from '../../../src/events.js';
 import CONSTANTS from '../../../src/constants.json';
 
@@ -50,20 +57,6 @@ function mockMessageFromClient(key) {
 let mockWrapper = `<wrapper>${htmlPlaceholder}</wrapper>`;
 
 describe('Geoedge RTD module', function () {
-  describe('beforeInit', function () {
-    let submoduleStub;
-
-    before(function () {
-      submoduleStub = sinon.stub(hook, 'submodule');
-    });
-    after(function () {
-      submoduleStub.restore();
-    });
-    it('should register RTD submodule provider', function () {
-      beforeInit();
-      expect(submoduleStub.calledWith('realTimeData', geoedgeSubmodule)).to.equal(true);
-    });
-  });
   describe('submodule', function () {
     describe('name', function () {
       it('should be geoedge', function () {
diff --git a/test/spec/modules/greenbidsRtdProvider_spec.js b/test/spec/modules/greenbidsRtdProvider_spec.js
index 7cb6c10ce48..cd93e9013c0 100644
--- a/test/spec/modules/greenbidsRtdProvider_spec.js
+++ b/test/spec/modules/greenbidsRtdProvider_spec.js
@@ -6,18 +6,9 @@ import {
 import {
   greenbidsSubmodule
 } from 'modules/greenbidsRtdProvider.js';
+import {server} from '../../mocks/xhr.js';
 
 describe('greenbidsRtdProvider', () => {
-  let server;
-
-  beforeEach(() => {
-    server = sinon.createFakeServer();
-  });
-
-  afterEach(() => {
-    server.restore();
-  });
-
   const endPoint = 't.greenbids.ai';
 
   const SAMPLE_MODULE_CONFIG = {
@@ -137,7 +128,6 @@ describe('greenbidsRtdProvider', () => {
           {'Content-Type': 'application/json'},
           JSON.stringify(SAMPLE_RESPONSE_ADUNITS)
         );
-        done();
       }, 50);
 
       setTimeout(() => {
@@ -152,6 +142,7 @@ describe('greenbidsRtdProvider', () => {
         expect(requestBids.adUnits[1].bids.map((bid) => bid.bidder)).to.include('rubicon');
         expect(requestBids.adUnits[1].bids.map((bid) => bid.bidder)).to.include('openx');
         expect(callback.calledOnce).to.be.true;
+        done();
       }, 60);
     });
   });
@@ -195,7 +186,6 @@ describe('greenbidsRtdProvider', () => {
           {'Content-Type': 'application/json'},
           JSON.stringify({'failure': 'fail'})
         );
-        done();
       }, 50);
 
       setTimeout(() => {
@@ -204,6 +194,7 @@ describe('greenbidsRtdProvider', () => {
         expect(requestBids.adUnits[0].bids).to.have.length(3);
         expect(requestBids.adUnits[1].bids).to.have.length(3);
         expect(callback.calledOnce).to.be.true;
+        done();
       }, 60);
     });
   });
diff --git a/test/spec/modules/hadronIdSystem_spec.js b/test/spec/modules/hadronIdSystem_spec.js
index c998ef2cf14..cc0118d4659 100644
--- a/test/spec/modules/hadronIdSystem_spec.js
+++ b/test/spec/modules/hadronIdSystem_spec.js
@@ -47,7 +47,7 @@ describe('HadronIdSystem', function () {
       const callback = hadronIdSubmodule.getId(config).callback;
       callback(callbackSpy);
       const request = server.requests[0];
-      expect(request.url).to.eq('https://hadronid.publync.com?partner_id=0&_it=prebid');
+      expect(request.url).to.eq('https://hadronid.publync.com/?partner_id=0&_it=prebid');
       request.respond(200, { 'Content-Type': 'application/json' }, JSON.stringify({ hadronId: 'testHadronId1' }));
       expect(callbackSpy.lastCall.lastArg).to.deep.equal({ id: { hadronId: 'testHadronId1' } });
     });
diff --git a/test/spec/modules/id5AnalyticsAdapter_spec.js b/test/spec/modules/id5AnalyticsAdapter_spec.js
index 83951c3a6e9..9cb7233ce7c 100644
--- a/test/spec/modules/id5AnalyticsAdapter_spec.js
+++ b/test/spec/modules/id5AnalyticsAdapter_spec.js
@@ -1,20 +1,18 @@
 import adapterManager from '../../../src/adapterManager.js';
 import id5AnalyticsAdapter from '../../../modules/id5AnalyticsAdapter.js';
 import { expect } from 'chai';
-import sinon from 'sinon';
 import * as events from '../../../src/events.js';
 import constants from '../../../src/constants.json';
 import { generateUUID } from '../../../src/utils.js';
+import {server} from '../../mocks/xhr.js';
 
 const CONFIG_URL = 'https://api.id5-sync.com/analytics/12349/pbjs';
 const INGEST_URL = 'https://test.me/ingest';
 
 describe('ID5 analytics adapter', () => {
-  let server;
   let config;
 
   beforeEach(() => {
-    server = sinon.createFakeServer();
     config = {
       options: {
         partnerId: 12349,
@@ -22,10 +20,6 @@ describe('ID5 analytics adapter', () => {
     };
   });
 
-  afterEach(() => {
-    server.restore();
-  });
-
   it('registers itself with the adapter manager', () => {
     const adapter = adapterManager.getAnalyticsAdapter('id5Analytics');
     expect(adapter).to.exist;
diff --git a/test/spec/modules/id5IdSystem_spec.js b/test/spec/modules/id5IdSystem_spec.js
index 2d81c9b7b8d..dd284357abe 100644
--- a/test/spec/modules/id5IdSystem_spec.js
+++ b/test/spec/modules/id5IdSystem_spec.js
@@ -19,8 +19,8 @@ import {uspDataHandler} from 'src/adapterManager.js';
 import 'src/prebid.js';
 import {hook} from '../../../src/hook.js';
 import {mockGdprConsent} from '../../helpers/consentData.js';
-
-let expect = require('chai').expect;
+import {server} from '../../mocks/xhr.js';
+import {expect} from 'chai';
 
 describe('ID5 ID System', function () {
   const ID5_MODULE_NAME = 'id5Id';
@@ -268,7 +268,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server and handle a valid response', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let config = getId5FetchConfig();
       let submoduleResponse = callSubmoduleGetId(config, undefined, undefined);
 
@@ -297,7 +297,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server with gdpr data ', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let consentData = {
         gdprApplies: true,
         consentString: 'consentString',
@@ -322,7 +322,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server without gdpr data when gdpr not applies ', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let consentData = {
         gdprApplies: false,
         consentString: 'consentString'
@@ -347,7 +347,7 @@ describe('ID5 ID System', function () {
     it('should call the ID5 server with us privacy consent', function () {
       let usPrivacyString = '1YN-';
       uspDataHandler.setConsentData(usPrivacyString)
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let consentData = {
         gdprApplies: true,
         consentString: 'consentString',
@@ -371,7 +371,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server with no signature field when no stored object', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let submoduleResponse = callSubmoduleGetId(getId5FetchConfig(), undefined, undefined);
 
       return xhrServerMock.expectFetchRequest()
@@ -384,7 +384,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server for config with submodule config object', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let id5FetchConfig = getId5FetchConfig();
       id5FetchConfig.params.extraParam = {
         x: 'X',
@@ -408,7 +408,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server for config with partner id being a string', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let id5FetchConfig = getId5FetchConfig();
       id5FetchConfig.params.partner = '173';
       let submoduleResponse = callSubmoduleGetId(id5FetchConfig, undefined, undefined);
@@ -426,7 +426,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server for config with overridden url', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let id5FetchConfig = getId5FetchConfig();
       id5FetchConfig.params.configUrl = 'http://localhost/x/y/z'
 
@@ -444,7 +444,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server with additional data when provided', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let submoduleResponse = callSubmoduleGetId(getId5FetchConfig(), undefined, undefined);
 
       return xhrServerMock.expectConfigRequest()
@@ -478,7 +478,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server with extensions', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let submoduleResponse = callSubmoduleGetId(getId5FetchConfig(), undefined, undefined);
 
       return xhrServerMock.expectConfigRequest()
@@ -515,7 +515,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server with extensions fetched with POST', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let submoduleResponse = callSubmoduleGetId(getId5FetchConfig(), undefined, undefined);
 
       return xhrServerMock.expectConfigRequest()
@@ -561,7 +561,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server with signature field from stored object', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let submoduleResponse = callSubmoduleGetId(getId5FetchConfig(), undefined, ID5_STORED_OBJ);
 
       return xhrServerMock.expectFetchRequest()
@@ -574,7 +574,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server with pd field when pd config is set', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       const pubData = 'b50ca08271795a8e7e4012813f23d505193d75c0f2e2bb99baa63aa822f66ed3';
 
       let id5Config = getId5FetchConfig();
@@ -592,7 +592,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server with no pd field when pd config is not set', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let id5Config = getId5FetchConfig();
       id5Config.params.pd = undefined;
 
@@ -608,7 +608,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server with nb=1 when no stored value exists and reset after', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       coreStorage.removeDataFromLocalStorage(ID5_NB_STORAGE_NAME);
 
       let submoduleResponse = callSubmoduleGetId(getId5FetchConfig(), undefined, ID5_STORED_OBJ);
@@ -626,7 +626,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server with incremented nb when stored value exists and reset after', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       storeNbInCache(ID5_TEST_PARTNER_ID, 1);
 
       let submoduleResponse = callSubmoduleGetId(getId5FetchConfig(), undefined, ID5_STORED_OBJ);
@@ -644,7 +644,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server with ab_testing object when abTesting is turned on', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let id5Config = getId5FetchConfig();
       id5Config.params.abTesting = {enabled: true, controlGroupPct: 0.234}
 
@@ -661,7 +661,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server without ab_testing object when abTesting is turned off', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let id5Config = getId5FetchConfig();
       id5Config.params.abTesting = {enabled: false, controlGroupPct: 0.55}
 
@@ -677,7 +677,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call the ID5 server without ab_testing when when abTesting is not set', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let id5Config = getId5FetchConfig();
 
       let submoduleResponse = callSubmoduleGetId(id5Config, undefined, ID5_STORED_OBJ);
@@ -692,7 +692,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should store the privacy object from the ID5 server response', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let submoduleResponse = callSubmoduleGetId(getId5FetchConfig(), undefined, ID5_STORED_OBJ);
 
       const privacy = {
@@ -714,7 +714,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should not store a privacy object if not part of ID5 server response', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       coreStorage.removeDataFromLocalStorage(ID5_PRIVACY_STORAGE_NAME);
       let submoduleResponse = callSubmoduleGetId(getId5FetchConfig(), undefined, ID5_STORED_OBJ);
 
@@ -760,7 +760,7 @@ describe('ID5 ID System', function () {
       [false, 0]
     ].forEach(function ([isEnabled, expectedValue]) {
       it(`should check localStorage availability and log in request. Available=${isEnabled}`, () => {
-        let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+        let xhrServerMock = new XhrServerMock(server)
         let config = getId5FetchConfig();
         let submoduleResponse = callSubmoduleGetId(config, undefined, undefined);
         storage.localStorageIsEnabled.callsFake(() => isEnabled)
@@ -878,7 +878,7 @@ describe('ID5 ID System', function () {
     });
 
     it('should call ID5 servers with signature and incremented nb post auction if refresh needed', function () {
-      let xhrServerMock = new XhrServerMock(sinon.createFakeServer())
+      let xhrServerMock = new XhrServerMock(server)
       let initialLocalStorageValue = JSON.stringify(ID5_STORED_OBJ);
       storeInLocalStorage(ID5_STORAGE_NAME, initialLocalStorageValue, 1);
       storeInLocalStorage(`${ID5_STORAGE_NAME}_last`, expDaysStr(-1), 1);
diff --git a/test/spec/modules/identityLinkIdSystem_spec.js b/test/spec/modules/identityLinkIdSystem_spec.js
index 52e9f9171d6..9777ebe5501 100644
--- a/test/spec/modules/identityLinkIdSystem_spec.js
+++ b/test/spec/modules/identityLinkIdSystem_spec.js
@@ -111,10 +111,8 @@ describe('IdentityLinkId tests', function () {
     request.respond(
       204,
       responseHeader,
-      ''
     );
     expect(callBackSpy.calledOnce).to.be.true;
-    expect(request.response).to.equal('');
     expect(logErrorStub.calledOnce).to.not.be.true;
   });
 
diff --git a/test/spec/modules/intentIqIdSystem_spec.js b/test/spec/modules/intentIqIdSystem_spec.js
index d5ffbf92d68..ef174af416b 100644
--- a/test/spec/modules/intentIqIdSystem_spec.js
+++ b/test/spec/modules/intentIqIdSystem_spec.js
@@ -169,10 +169,8 @@ describe('IntentIQ tests', function () {
     request.respond(
       204,
       responseHeader,
-      ''
     );
     expect(callBackSpy.calledOnce).to.be.true;
-    expect(request.response).to.equal('');
   });
 
   it('should log an error and continue to callback if ajax request errors', function () {
diff --git a/test/spec/modules/invisiblyAnalyticsAdapter_spec.js b/test/spec/modules/invisiblyAnalyticsAdapter_spec.js
index 2c460156318..a8828515ffd 100644
--- a/test/spec/modules/invisiblyAnalyticsAdapter_spec.js
+++ b/test/spec/modules/invisiblyAnalyticsAdapter_spec.js
@@ -1,6 +1,7 @@
 import invisiblyAdapter from 'modules/invisiblyAnalyticsAdapter.js';
 import { expect } from 'chai';
 import {expectEvents} from '../../helpers/analytics.js';
+import {server} from '../../mocks/xhr.js';
 let events = require('src/events');
 let constants = require('src/constants.json');
 
@@ -169,11 +170,7 @@ describe('Invisibly Analytics Adapter test suite', function () {
 
   describe('Invisibly Analytic tests specs', function () {
     beforeEach(function () {
-      xhr = sinon.useFakeXMLHttpRequest();
-      requests = [];
-      xhr.onCreate = (xhr) => {
-        requests.push(xhr);
-      };
+      requests = server.requests;
       sinon.stub(events, 'getEvents').returns([]);
       sinon.spy(invisiblyAdapter, 'track');
     });
@@ -182,7 +179,6 @@ describe('Invisibly Analytics Adapter test suite', function () {
       invisiblyAdapter.disableAnalytics();
       events.getEvents.restore();
       invisiblyAdapter.track.restore();
-      xhr.restore();
     });
 
     describe('Send all events as & when they are captured', function () {
diff --git a/test/spec/modules/jwplayerRtdProvider_spec.js b/test/spec/modules/jwplayerRtdProvider_spec.js
index 5a38a971e09..4638595e0d6 100644
--- a/test/spec/modules/jwplayerRtdProvider_spec.js
+++ b/test/spec/modules/jwplayerRtdProvider_spec.js
@@ -1,8 +1,19 @@
-import { fetchTargetingForMediaId, getVatFromCache, extractPublisherParams,
-  formatTargetingResponse, getVatFromPlayer, enrichAdUnits, addTargetingToBid,
-  fetchTargetingInformation, jwplayerSubmodule, getContentId, getContentSegments, getContentData, addOrtbSiteContent } from 'modules/jwplayerRtdProvider.js';
-import { server } from 'test/mocks/xhr.js';
-import { config as prebidConfig } from 'src/config.js';
+import {
+  addOrtbSiteContent,
+  addTargetingToBid,
+  enrichAdUnits,
+  extractPublisherParams,
+  fetchTargetingForMediaId,
+  fetchTargetingInformation,
+  formatTargetingResponse,
+  getContentData,
+  getContentId,
+  getContentSegments,
+  getVatFromCache,
+  getVatFromPlayer,
+  jwplayerSubmodule
+} from 'modules/jwplayerRtdProvider.js';
+import {server} from 'test/mocks/xhr.js';
 import {deepClone} from '../../../src/utils.js';
 
 describe('jwplayerRtdProvider', function() {
@@ -223,9 +234,6 @@ describe('jwplayerRtdProvider', function() {
       describe('Get Bid Request Data', function () {
         it('executes immediately while request is active if player has item', function () {
           const bidRequestSpy = sinon.spy();
-          const fakeServer = sinon.createFakeServer();
-          fakeServer.respondImmediately = false;
-          fakeServer.autoRespond = false;
 
           fetchTargetingForMediaId(mediaIdWithSegment);
 
@@ -255,7 +263,7 @@ describe('jwplayerRtdProvider', function() {
           jwplayerSubmodule.getBidRequestData({ adUnits: [adUnit] }, bidRequestSpy);
           expect(bidRequestSpy.calledOnce).to.be.true;
           expect(bid.rtd.jwplayer).to.have.deep.property('targeting', expectedTargeting);
-          fakeServer.respond();
+          server.respond();
           expect(bidRequestSpy.calledOnce).to.be.true;
         });
       });
@@ -271,22 +279,17 @@ describe('jwplayerRtdProvider', function() {
       }
     };
     let bidRequestSpy;
-    let fakeServer;
     let clock;
 
     beforeEach(function () {
       bidRequestSpy = sinon.spy();
 
-      fakeServer = sinon.createFakeServer();
-      fakeServer.respondImmediately = false;
-      fakeServer.autoRespond = false;
-
       clock = sinon.useFakeTimers();
     });
 
     afterEach(function () {
       clock.restore();
-      fakeServer.respond();
+      server.respond();
     });
 
     it('adds targeting when pending request succeeds', function () {
@@ -318,7 +321,7 @@ describe('jwplayerRtdProvider', function() {
       expect(bid1).to.not.have.property('rtd');
       expect(bid2).to.not.have.property('rtd');
 
-      const request = fakeServer.requests[0];
+      const request = server.requests[0];
       request.respond(
         200,
         responseHeader,
@@ -358,7 +361,7 @@ describe('jwplayerRtdProvider', function() {
         },
         bids
       };
-      const request = fakeServer.requests[0];
+      const request = server.requests[0];
       request.respond(
         200,
         responseHeader,
@@ -443,7 +446,7 @@ describe('jwplayerRtdProvider', function() {
       expect(bid1).to.not.have.property('rtd');
       expect(bid2).to.not.have.property('rtd');
 
-      const request = fakeServer.requests[0];
+      const request = server.requests[0];
       request.respond(
         200,
         responseHeader,
@@ -518,7 +521,7 @@ describe('jwplayerRtdProvider', function() {
       const bid1 = bids[0];
       expect(bid1).to.not.have.property('rtd');
 
-      const request = fakeServer.requests[0];
+      const request = server.requests[0];
       request.respond(
         200,
         responseHeader,
@@ -931,7 +934,6 @@ describe('jwplayerRtdProvider', function() {
     describe('Get Bid Request Data', function () {
       const validMediaIDs = ['media_ID_1', 'media_ID_2', 'media_ID_3'];
       let bidRequestSpy;
-      let fakeServer;
       let clock;
       let bidReqConfig;
 
@@ -971,16 +973,12 @@ describe('jwplayerRtdProvider', function() {
 
         bidRequestSpy = sinon.spy();
 
-        fakeServer = sinon.createFakeServer();
-        fakeServer.respondImmediately = false;
-        fakeServer.autoRespond = false;
-
         clock = sinon.useFakeTimers();
       });
 
       afterEach(function () {
         clock.restore();
-        fakeServer.respond();
+        server.respond();
       });
 
       it('executes callback immediately when ad units are missing', function () {
@@ -1003,9 +1001,9 @@ describe('jwplayerRtdProvider', function() {
         jwplayerSubmodule.getBidRequestData(bidReqConfig, bidRequestSpy);
         expect(bidRequestSpy.notCalled).to.be.true;
 
-        const req1 = fakeServer.requests[0];
-        const req2 = fakeServer.requests[1];
-        const req3 = fakeServer.requests[2];
+        const req1 = server.requests[0];
+        const req2 = server.requests[1];
+        const req3 = server.requests[2];
 
         req1.respond();
         expect(bidRequestSpy.notCalled).to.be.true;
diff --git a/test/spec/modules/magniteAnalyticsAdapter_spec.js b/test/spec/modules/magniteAnalyticsAdapter_spec.js
index ae63f19f46b..304ce2ed7a5 100644
--- a/test/spec/modules/magniteAnalyticsAdapter_spec.js
+++ b/test/spec/modules/magniteAnalyticsAdapter_spec.js
@@ -550,7 +550,7 @@ describe('magnite analytics adapter', function () {
       expect(server.requests.length).to.equal(1);
       let request = server.requests[0];
 
-      expect(request.url).to.equal('//localhost:9999/event');
+      expect(request.url).to.match(/\/\/localhost:9999\/event/);
 
       let message = JSON.parse(request.requestBody);
 
@@ -724,7 +724,7 @@ describe('magnite analytics adapter', function () {
         expect(server.requests.length).to.equal(1);
         let request = server.requests[0];
 
-        expect(request.url).to.equal('//localhost:9999/event');
+        expect(request.url).to.match(/\/\/localhost:9999\/event/);
 
         let message = JSON.parse(request.requestBody);
 
diff --git a/test/spec/modules/mgidRtdProvider_spec.js b/test/spec/modules/mgidRtdProvider_spec.js
index 4f70b4d8b7c..996875649b6 100644
--- a/test/spec/modules/mgidRtdProvider_spec.js
+++ b/test/spec/modules/mgidRtdProvider_spec.js
@@ -1,16 +1,14 @@
 import { mgidSubmodule, storage } from '../../../modules/mgidRtdProvider.js';
 import {expect} from 'chai';
 import * as refererDetection from '../../../src/refererDetection';
+import {server} from '../../mocks/xhr.js';
 
 describe('Mgid RTD submodule', () => {
-  let server;
   let clock;
   let getRefererInfoStub;
   let getDataFromLocalStorageStub;
 
   beforeEach(() => {
-    server = sinon.fakeServer.create();
-
     clock = sinon.useFakeTimers();
 
     getRefererInfoStub = sinon.stub(refererDetection, 'getRefererInfo');
@@ -22,7 +20,6 @@ describe('Mgid RTD submodule', () => {
   });
 
   afterEach(() => {
-    server.restore();
     clock.restore();
     getRefererInfoStub.restore();
     getDataFromLocalStorageStub.restore();
@@ -309,7 +306,6 @@ describe('Mgid RTD submodule', () => {
     server.requests[0].respond(
       204,
       {'Content-Type': 'application/json'},
-      '{}'
     );
 
     assert.deepEqual(reqBidsConfigObj.ortb2Fragments.global, {});
diff --git a/test/spec/modules/oguryBidAdapter_spec.js b/test/spec/modules/oguryBidAdapter_spec.js
index bbe53855094..ed358af19b6 100644
--- a/test/spec/modules/oguryBidAdapter_spec.js
+++ b/test/spec/modules/oguryBidAdapter_spec.js
@@ -1,6 +1,7 @@
 import { expect } from 'chai';
 import { spec } from 'modules/oguryBidAdapter';
 import * as utils from 'src/utils.js';
+import {server} from '../../mocks/xhr.js';
 
 const BID_URL = 'https://mweb-hb.presage.io/api/header-bidding-request';
 const TIMEOUT_URL = 'https://ms-ads-monitoring-events.presage.io/bid_timeout'
@@ -851,20 +852,11 @@ describe('OguryBidAdapter', function () {
   });
 
   describe('onBidWon', function() {
-    const nurl = 'https://fakewinurl.test';
-    let xhr;
+    const nurl = 'https://fakewinurl.test/';
     let requests;
 
     beforeEach(function() {
-      xhr = sinon.useFakeXMLHttpRequest();
-      requests = [];
-      xhr.onCreate = (xhr) => {
-        requests.push(xhr);
-      };
-    })
-
-    afterEach(function() {
-      xhr.restore()
+      requests = server.requests;
     })
 
     it('Should not create nurl request if bid is undefined', function() {
@@ -932,21 +924,15 @@ describe('OguryBidAdapter', function () {
   })
 
   describe('onTimeout', function () {
-    let xhr;
     let requests;
 
     beforeEach(function() {
-      xhr = sinon.useFakeXMLHttpRequest();
-      requests = [];
-      xhr.onCreate = (xhr) => {
+      requests = server.requests;
+      server.onCreate = (xhr) => {
         requests.push(xhr);
       };
     })
 
-    afterEach(function() {
-      xhr.restore()
-    })
-
     it('should send on bid timeout notification', function() {
       const bid = {
         ad: '<img style="width: 300px; height: 250px;" src="https://assets.afcdn.com/recipe/20190529/93153_w1024h768c1cx2220cy1728cxt0cyt0cxb4441cyb3456.jpg" alt="cookies" />',
diff --git a/test/spec/modules/ooloAnalyticsAdapter_spec.js b/test/spec/modules/ooloAnalyticsAdapter_spec.js
index 2515c713b14..1224c3f0740 100644
--- a/test/spec/modules/ooloAnalyticsAdapter_spec.js
+++ b/test/spec/modules/ooloAnalyticsAdapter_spec.js
@@ -663,7 +663,7 @@ describe('oolo Prebid Analytic', () => {
 
       events.emit(constants.EVENTS.AUCTION_INIT, { ...auctionInit });
 
-      expect(server.requests[3].url).to.equal('https://pbjs.com')
+      expect(server.requests[3].url).to.equal('https://pbjs.com/')
     })
 
     it('should send raw events based on server configuration', () => {
diff --git a/test/spec/modules/prebidServerBidAdapter_spec.js b/test/spec/modules/prebidServerBidAdapter_spec.js
index e4f06c8835f..1626d6f2c9d 100644
--- a/test/spec/modules/prebidServerBidAdapter_spec.js
+++ b/test/spec/modules/prebidServerBidAdapter_spec.js
@@ -6,7 +6,7 @@ import {
   resetWurlMap,
   s2sDefaultConfig
 } from 'modules/prebidServerBidAdapter/index.js';
-import adapterManager from 'src/adapterManager.js';
+import adapterManager, {PBS_ADAPTER_NAME} from 'src/adapterManager.js';
 import * as utils from 'src/utils.js';
 import {deepAccess, deepClone, mergeDeep} from 'src/utils.js';
 import {ajax} from 'src/ajax.js';
@@ -27,6 +27,7 @@ import 'modules/consentManagementUsp.js';
 import 'modules/schain.js';
 import 'modules/fledgeForGpt.js';
 import * as redactor from 'src/activities/redactor.js';
+import * as activityRules from 'src/activities/rules.js';
 import {hook} from '../../../src/hook.js';
 import {decorateAdUnitsWithNativeParams} from '../../../src/native.js';
 import {auctionManager} from '../../../src/auctionManager.js';
@@ -35,6 +36,10 @@ import {addComponentAuction, registerBidder} from 'src/adapters/bidderFactory.js
 import {getGlobal} from '../../../src/prebidGlobal.js';
 import {syncAddFPDEnrichments, syncAddFPDToBidderRequest} from '../../helpers/fpd.js';
 import {deepSetValue} from '../../../src/utils.js';
+import {sandbox} from 'sinon';
+import {ACTIVITY_TRANSMIT_UFPD} from '../../../src/activities/activities.js';
+import {activityParams} from '../../../src/activities/activityParams.js';
+import {MODULE_TYPE_PREBID} from '../../../src/activities/modules.js';
 
 let CONFIG = {
   accountId: '1',
@@ -734,13 +739,39 @@ describe('S2S Adapter', function () {
       })
     })
 
+    describe('browsingTopics', () => {
+      const sandbox = sinon.createSandbox();
+      afterEach(() => {
+        sandbox.restore()
+      });
+      Object.entries({
+        'allowed': true,
+        'not allowed': false,
+      }).forEach(([t, allow]) => {
+        it(`should be set to ${allow} when transmitUfpd is ${t}`, () => {
+          sandbox.stub(activityRules, 'isActivityAllowed').callsFake((activity, params) => {
+            if (activity === ACTIVITY_TRANSMIT_UFPD && params.component === `${MODULE_TYPE_PREBID}.${PBS_ADAPTER_NAME}`) {
+              return allow;
+            }
+            return false;
+          });
+          config.setConfig({s2sConfig: CONFIG});
+          const ajax = sinon.stub();
+          adapter.callBids(REQUEST, BID_REQUESTS, addBidResponse, done, ajax);
+          sinon.assert.calledWith(ajax, sinon.match.any, sinon.match.any, sinon.match.any, sinon.match({
+            browsingTopics: allow
+          }));
+        });
+      });
+    })
+
     it('should set tmax to s2sConfig.timeout', () => {
       const cfg = {...CONFIG, timeout: 123};
       config.setConfig({s2sConfig: cfg});
       adapter.callBids({...REQUEST, s2sConfig: cfg}, BID_REQUESTS, addBidResponse, done, ajax);
       const req = JSON.parse(server.requests[0].requestBody);
       expect(req.tmax).to.eql(123);
-    })
+    });
 
     it('should block request if config did not define p1Consent URL in endpoint object config', function () {
       let badConfig = utils.deepClone(CONFIG);
diff --git a/test/spec/modules/priceFloors_spec.js b/test/spec/modules/priceFloors_spec.js
index 64c871308a9..e2b8ca38792 100644
--- a/test/spec/modules/priceFloors_spec.js
+++ b/test/spec/modules/priceFloors_spec.js
@@ -22,6 +22,7 @@ import {auctionManager} from '../../../src/auctionManager.js';
 import {stubAuctionIndex} from '../../helpers/indexStub.js';
 import {guardTids} from '../../../src/adapters/bidderFactory.js';
 import * as activities from '../../../src/activities/rules.js';
+import {server} from '../../mocks/xhr.js';
 
 describe('the price floors module', function () {
   let logErrorSpy;
@@ -593,16 +594,11 @@ describe('the price floors module', function () {
         adUnits,
       });
     };
-    let fakeFloorProvider;
     let actualAllowedFields = allowedFields;
     let actualFieldMatchingFunctions = fieldMatchingFunctions;
     const defaultAllowedFields = [...allowedFields];
     const defaultMatchingFunctions = {...fieldMatchingFunctions};
-    beforeEach(function() {
-      fakeFloorProvider = sinon.fakeServer.create();
-    });
     afterEach(function() {
-      fakeFloorProvider.restore();
       exposedAdUnits = undefined;
       actualAllowedFields = [...defaultAllowedFields];
       actualFieldMatchingFunctions = {...defaultMatchingFunctions};
@@ -986,7 +982,7 @@ describe('the price floors module', function () {
       });
     });
     it('Should continue auction of delay is hit without a response from floor provider', function () {
-      handleSetFloorsConfig({...basicFloorConfig, auctionDelay: 250, endpoint: {url: 'http://www.fakeFloorProvider.json'}});
+      handleSetFloorsConfig({...basicFloorConfig, auctionDelay: 250, endpoint: {url: 'http://www.fakefloorprovider.json//'}});
 
       // start the auction it should delay and not immediately call `continueAuction`
       runStandardAuction();
@@ -1013,7 +1009,7 @@ describe('the price floors module', function () {
         fetchStatus: 'timeout',
         floorProvider: undefined
       });
-      fakeFloorProvider.respond();
+      server.respond();
     });
     it('It should fetch if config has url and bidRequests have fetch level flooring meta data', function () {
       // init the fake server with response stuff
@@ -1021,14 +1017,14 @@ describe('the price floors module', function () {
         ...basicFloorData,
         modelVersion: 'fetch model name', // change the model name
       };
-      fakeFloorProvider.respondWith(JSON.stringify(fetchFloorData));
+      server.respondWith(JSON.stringify(fetchFloorData));
 
       // run setConfig indicating fetch
-      handleSetFloorsConfig({...basicFloorConfig, floorProvider: 'floorprovider', auctionDelay: 250, endpoint: {url: 'http://www.fakeFloorProvider.json'}});
+      handleSetFloorsConfig({...basicFloorConfig, floorProvider: 'floorprovider', auctionDelay: 250, endpoint: {url: 'http://www.fakefloorprovider.json/'}});
 
       // floor provider should be called
-      expect(fakeFloorProvider.requests.length).to.equal(1);
-      expect(fakeFloorProvider.requests[0].url).to.equal('http://www.fakeFloorProvider.json');
+      expect(server.requests.length).to.equal(1);
+      expect(server.requests[0].url).to.equal('http://www.fakefloorprovider.json/');
 
       // start the auction it should delay and not immediately call `continueAuction`
       runStandardAuction();
@@ -1037,7 +1033,7 @@ describe('the price floors module', function () {
       expect(exposedAdUnits).to.be.undefined;
 
       // make the fetch respond
-      fakeFloorProvider.respond();
+      server.respond();
       expect(exposedAdUnits).to.not.be.undefined;
 
       // the exposedAdUnits should be from the fetch not setConfig level data
@@ -1061,14 +1057,14 @@ describe('the price floors module', function () {
         floorProvider: 'floorProviderD', // change the floor provider
         modelVersion: 'fetch model name', // change the model name
       };
-      fakeFloorProvider.respondWith(JSON.stringify(fetchFloorData));
+      server.respondWith(JSON.stringify(fetchFloorData));
 
       // run setConfig indicating fetch
-      handleSetFloorsConfig({...basicFloorConfig, floorProvider: 'floorproviderC', auctionDelay: 250, endpoint: {url: 'http://www.fakeFloorProvider.json'}});
+      handleSetFloorsConfig({...basicFloorConfig, floorProvider: 'floorproviderC', auctionDelay: 250, endpoint: {url: 'http://www.fakefloorprovider.json/'}});
 
       // floor provider should be called
-      expect(fakeFloorProvider.requests.length).to.equal(1);
-      expect(fakeFloorProvider.requests[0].url).to.equal('http://www.fakeFloorProvider.json');
+      expect(server.requests.length).to.equal(1);
+      expect(server.requests[0].url).to.equal('http://www.fakefloorprovider.json/');
 
       // start the auction it should delay and not immediately call `continueAuction`
       runStandardAuction();
@@ -1077,7 +1073,7 @@ describe('the price floors module', function () {
       expect(exposedAdUnits).to.be.undefined;
 
       // make the fetch respond
-      fakeFloorProvider.respond();
+      server.respond();
 
       // the exposedAdUnits should be from the fetch not setConfig level data
       // and fetchStatus is success since fetch worked
@@ -1102,14 +1098,14 @@ describe('the price floors module', function () {
         modelVersion: 'fetch model name', // change the model name
       };
       fetchFloorData.skipRate = 95;
-      fakeFloorProvider.respondWith(JSON.stringify(fetchFloorData));
+      server.respondWith(JSON.stringify(fetchFloorData));
 
       // run setConfig indicating fetch
-      handleSetFloorsConfig({...basicFloorConfig, floorProvider: 'floorprovider', auctionDelay: 250, endpoint: {url: 'http://www.fakeFloorProvider.json'}});
+      handleSetFloorsConfig({...basicFloorConfig, floorProvider: 'floorprovider', auctionDelay: 250, endpoint: {url: 'http://www.fakefloorprovider.json/'}});
 
       // floor provider should be called
-      expect(fakeFloorProvider.requests.length).to.equal(1);
-      expect(fakeFloorProvider.requests[0].url).to.equal('http://www.fakeFloorProvider.json');
+      expect(server.requests.length).to.equal(1);
+      expect(server.requests[0].url).to.equal('http://www.fakefloorprovider.json/');
 
       // start the auction it should delay and not immediately call `continueAuction`
       runStandardAuction();
@@ -1118,7 +1114,7 @@ describe('the price floors module', function () {
       expect(exposedAdUnits).to.be.undefined;
 
       // make the fetch respond
-      fakeFloorProvider.respond();
+      server.respond();
       expect(exposedAdUnits).to.not.be.undefined;
 
       // the exposedAdUnits should be from the fetch not setConfig level data
@@ -1137,10 +1133,10 @@ describe('the price floors module', function () {
     });
     it('Should not break if floor provider returns 404', function () {
       // run setConfig indicating fetch
-      handleSetFloorsConfig({...basicFloorConfig, auctionDelay: 250, endpoint: {url: 'http://www.fakeFloorProvider.json'}});
+      handleSetFloorsConfig({...basicFloorConfig, auctionDelay: 250, endpoint: {url: 'http://www.fakefloorprovider.json/'}});
 
       // run the auction and make server respond with 404
-      fakeFloorProvider.respond();
+      server.respond();
       runStandardAuction();
 
       // error should have been called for fetch error
@@ -1160,13 +1156,13 @@ describe('the price floors module', function () {
       });
     });
     it('Should not break if floor provider returns non json', function () {
-      fakeFloorProvider.respondWith('Not valid response');
+      server.respondWith('Not valid response');
 
       // run setConfig indicating fetch
-      handleSetFloorsConfig({...basicFloorConfig, auctionDelay: 250, endpoint: {url: 'http://www.fakeFloorProvider.json'}});
+      handleSetFloorsConfig({...basicFloorConfig, auctionDelay: 250, endpoint: {url: 'http://www.fakefloorprovider.json/'}});
 
       // run the auction and make server respond
-      fakeFloorProvider.respond();
+      server.respond();
       runStandardAuction();
 
       // error should have been called for response floor data not being valid
@@ -1187,27 +1183,27 @@ describe('the price floors module', function () {
     });
     it('should handle not using fetch correctly', function () {
       // run setConfig twice indicating fetch
-      fakeFloorProvider.respondWith(JSON.stringify(basicFloorData));
-      handleSetFloorsConfig({...basicFloorConfig, auctionDelay: 250, endpoint: {url: 'http://www.fakeFloorProvider.json'}});
-      handleSetFloorsConfig({...basicFloorConfig, auctionDelay: 250, endpoint: {url: 'http://www.fakeFloorProvider.json'}});
+      server.respondWith(JSON.stringify(basicFloorData));
+      handleSetFloorsConfig({...basicFloorConfig, auctionDelay: 250, endpoint: {url: 'http://www.fakefloorprovider.json/'}});
+      handleSetFloorsConfig({...basicFloorConfig, auctionDelay: 250, endpoint: {url: 'http://www.fakefloorprovider.json/'}});
 
       // log warn should be called and server only should have one request
       expect(logWarnSpy.calledOnce).to.equal(true);
-      expect(fakeFloorProvider.requests.length).to.equal(1);
-      expect(fakeFloorProvider.requests[0].url).to.equal('http://www.fakeFloorProvider.json');
+      expect(server.requests.length).to.equal(1);
+      expect(server.requests[0].url).to.equal('http://www.fakefloorprovider.json/');
 
       // now we respond and then run again it should work and make another request
-      fakeFloorProvider.respond();
-      handleSetFloorsConfig({...basicFloorConfig, auctionDelay: 250, endpoint: {url: 'http://www.fakeFloorProvider.json'}});
-      fakeFloorProvider.respond();
+      server.respond();
+      handleSetFloorsConfig({...basicFloorConfig, auctionDelay: 250, endpoint: {url: 'http://www.fakefloorprovider.json/'}});
+      server.respond();
 
       // now warn still only called once and server called twice
       expect(logWarnSpy.calledOnce).to.equal(true);
-      expect(fakeFloorProvider.requests.length).to.equal(2);
+      expect(server.requests.length).to.equal(2);
 
       // should log error if method is not GET for now
       expect(logErrorSpy.calledOnce).to.equal(false);
-      handleSetFloorsConfig({...basicFloorConfig, endpoint: {url: 'http://www.fakeFloorProvider.json', method: 'POST'}});
+      handleSetFloorsConfig({...basicFloorConfig, endpoint: {url: 'http://www.fakefloorprovider.json/', method: 'POST'}});
       expect(logErrorSpy.calledOnce).to.equal(true);
     });
     describe('isFloorsDataValid', function () {
diff --git a/test/spec/modules/publinkIdSystem_spec.js b/test/spec/modules/publinkIdSystem_spec.js
index 7d98b724bd8..f35a7453403 100644
--- a/test/spec/modules/publinkIdSystem_spec.js
+++ b/test/spec/modules/publinkIdSystem_spec.js
@@ -120,7 +120,7 @@ describe('PublinkIdSystem', () => {
         expect(parsed.search.mpn).to.equal('Prebid.js');
         expect(parsed.search.mpv).to.equal('$prebid.version$');
 
-        request.respond(204, {}, JSON.stringify(serverResponse));
+        request.respond(204);
         expect(callbackSpy.called).to.be.false;
       });
 
diff --git a/test/spec/modules/pubmaticAnalyticsAdapter_spec.js b/test/spec/modules/pubmaticAnalyticsAdapter_spec.js
index c56ed565c43..a676f3e3497 100755
--- a/test/spec/modules/pubmaticAnalyticsAdapter_spec.js
+++ b/test/spec/modules/pubmaticAnalyticsAdapter_spec.js
@@ -1,11 +1,10 @@
-import pubmaticAnalyticsAdapter, { getMetadata } from 'modules/pubmaticAnalyticsAdapter.js';
+import pubmaticAnalyticsAdapter, {getMetadata} from 'modules/pubmaticAnalyticsAdapter.js';
 import adapterManager from 'src/adapterManager.js';
 import CONSTANTS from 'src/constants.json';
-import { config } from 'src/config.js';
-import {
-  setConfig,
-  addBidResponseHook,
-} from 'modules/currency.js';
+import {config} from 'src/config.js';
+import {setConfig} from 'modules/currency.js';
+import {server} from '../../mocks/xhr.js';
+import 'src/prebid.js';
 
 let events = require('src/events');
 let ajax = require('src/ajax');
@@ -273,7 +272,6 @@ function getLoggerJsonFromRequest(requestBody) {
 
 describe('pubmatic analytics adapter', function () {
   let sandbox;
-  let xhr;
   let requests;
   let oldScreen;
   let clock;
@@ -282,9 +280,7 @@ describe('pubmatic analytics adapter', function () {
     setUADefault();
     sandbox = sinon.sandbox.create();
 
-    xhr = sandbox.useFakeXMLHttpRequest();
-    requests = [];
-    xhr.onCreate = request => requests.push(request);
+    requests = server.requests;
 
     sandbox.stub(events, 'getEvents').returns([]);
 
diff --git a/test/spec/modules/pubwiseAnalyticsAdapter_spec.js b/test/spec/modules/pubwiseAnalyticsAdapter_spec.js
index e14582edc39..92d5972cc13 100644
--- a/test/spec/modules/pubwiseAnalyticsAdapter_spec.js
+++ b/test/spec/modules/pubwiseAnalyticsAdapter_spec.js
@@ -1,6 +1,7 @@
 import {expect} from 'chai';
 import pubwiseAnalytics from 'modules/pubwiseAnalyticsAdapter.js';
 import {expectEvents} from '../../helpers/analytics.js';
+import {server} from '../../mocks/xhr.js';
 
 let events = require('src/events');
 let adapterManager = require('src/adapterManager').default;
@@ -9,7 +10,6 @@ let constants = require('src/constants.json');
 describe('PubWise Prebid Analytics', function () {
   let requests;
   let sandbox;
-  let xhr;
   let clock;
   let mock = {};
 
@@ -38,9 +38,7 @@ describe('PubWise Prebid Analytics', function () {
     clock = sandbox.useFakeTimers();
     sandbox.stub(events, 'getEvents').returns([]);
 
-    xhr = sandbox.useFakeXMLHttpRequest();
-    requests = [];
-    xhr.onCreate = request => requests.push(request);
+    requests = server.requests;
   });
 
   afterEach(function () {
@@ -50,10 +48,6 @@ describe('PubWise Prebid Analytics', function () {
   });
 
   describe('enableAnalytics', function () {
-    beforeEach(function () {
-      requests = [];
-    });
-
     it('should catch all events', function () {
       pubwiseAnalytics.enableAnalytics(mock.DEFAULT_PW_CONFIG);
 
diff --git a/test/spec/modules/teadsIdSystem_spec.js b/test/spec/modules/teadsIdSystem_spec.js
index 7b977e2fb2b..1959b990957 100644
--- a/test/spec/modules/teadsIdSystem_spec.js
+++ b/test/spec/modules/teadsIdSystem_spec.js
@@ -218,7 +218,7 @@ describe('TeadsIdSystem', function () {
       callback(callbackSpy);
       const request = server.requests[0];
       expect(request.url).to.include(teadsUrl);
-      request.respond(204, null, 'Unavailable');
+      request.respond(204);
       expect(logInfoStub.calledOnce).to.be.true;
     });
 
diff --git a/test/spec/modules/uid2IdSystem_helpers.js b/test/spec/modules/uid2IdSystem_helpers.js
index 65d52c1d7c3..5006a50dedd 100644
--- a/test/spec/modules/uid2IdSystem_helpers.js
+++ b/test/spec/modules/uid2IdSystem_helpers.js
@@ -1,6 +1,6 @@
-import { setConsentConfig } from 'modules/consentManagement.js';
-import { server } from 'test/mocks/xhr.js';
-import {coreStorage, init, setSubmoduleRegistry, requestBidsHook} from 'modules/userId/index.js';
+import {setConsentConfig} from 'modules/consentManagement.js';
+import {server} from 'test/mocks/xhr.js';
+import {coreStorage, requestBidsHook} from 'modules/userId/index.js';
 
 const msIn12Hours = 60 * 60 * 12 * 1000;
 const expireCookieDate = 'Thu, 01 Jan 1970 00:00:01 GMT';
@@ -34,8 +34,8 @@ export const apiHelpers = {
     refresh_expires: Date.now() + 24 * 60 * 60 * 1000, // 24 hours
     refresh_response_key: 'wR5t6HKMfJ2r4J7fEGX9Gw==', // Fake data
   }),
-  respondAfterDelay: (delay) => new Promise((resolve) => setTimeout(() => {
-    server.respond();
+  respondAfterDelay: (delay, srv = server) => new Promise((resolve) => setTimeout(() => {
+    srv.respond();
     setTimeout(() => resolve());
   }, delay)),
 }
diff --git a/test/spec/modules/uid2IdSystem_spec.js b/test/spec/modules/uid2IdSystem_spec.js
index 20a38a292bb..f33060869df 100644
--- a/test/spec/modules/uid2IdSystem_spec.js
+++ b/test/spec/modules/uid2IdSystem_spec.js
@@ -7,7 +7,6 @@ import { uid2IdSubmodule } from 'modules/uid2IdSystem.js';
 import 'src/prebid.js';
 import 'modules/consentManagement.js';
 import { getGlobal } from 'src/prebidGlobal.js';
-import { server } from 'test/mocks/xhr.js';
 import { configureTimerInterceptors } from 'test/mocks/timers.js';
 import { cookieHelpers, runAuction, apiHelpers, setGdprApplies } from './uid2IdSystem_helpers.js';
 import {hook} from 'src/hook.js';
@@ -56,22 +55,6 @@ const expectModuleStorageToContain = (initialIdentity, latestIdentity) => {
 const apiUrl = 'https://prod.uidapi.com/v2/token/refresh';
 const headers = { 'Content-Type': 'application/json' };
 const makeSuccessResponseBody = () => btoa(JSON.stringify({ status: 'success', body: { ...apiHelpers.makeTokenResponse(initialToken), advertising_token: refreshedToken } }));
-const configureUid2Response = (httpStatus, response) => server.respondWith('POST', apiUrl, (xhr) => xhr.respond(httpStatus, headers, response));
-const configureUid2ApiSuccessResponse = () => configureUid2Response(200, makeSuccessResponseBody());
-const configureUid2ApiFailResponse = () => configureUid2Response(500, 'Error');
-
-// Runs the provided test twice - once with a successful API mock, once with one which returns a server error
-const testApiSuccessAndFailure = (act, testDescription, failTestDescription, only = false) => {
-  const testFn = only ? it.only : it;
-  testFn(`API responds successfully: ${testDescription}`, async function() {
-    configureUid2ApiSuccessResponse();
-    await act(true);
-  });
-  testFn(`API responds with an error: ${failTestDescription ?? testDescription}`, async function() {
-    configureUid2ApiFailResponse();
-    await act(false);
-  });
-}
 
 const testCookieAndLocalStorage = (description, test, only = false) => {
   const describeFn = only ? describe.only : describe;
@@ -93,7 +76,7 @@ const testCookieAndLocalStorage = (description, test, only = false) => {
 };
 
 describe(`UID2 module`, function () {
-  let suiteSandbox, testSandbox, timerSpy, fullTestTitle, restoreSubtleToUndefined = false;
+  let server, suiteSandbox, testSandbox, timerSpy, fullTestTitle, restoreSubtleToUndefined = false;
   before(function () {
     timerSpy = configureTimerInterceptors(debugOutput);
     hook.ready();
@@ -116,13 +99,31 @@ describe(`UID2 module`, function () {
     if (restoreSubtleToUndefined) window.crypto.subtle = undefined;
   });
 
+  const configureUid2Response = (httpStatus, response) => server.respondWith('POST', apiUrl, (xhr) => xhr.respond(httpStatus, headers, response));
+  const configureUid2ApiSuccessResponse = () => configureUid2Response(200, makeSuccessResponseBody());
+  const configureUid2ApiFailResponse = () => configureUid2Response(500, 'Error');
+  // Runs the provided test twice - once with a successful API mock, once with one which returns a server error
+  const testApiSuccessAndFailure = (act, testDescription, failTestDescription, only = false) => {
+    const testFn = only ? it.only : it;
+    testFn(`API responds successfully: ${testDescription}`, async function() {
+      configureUid2ApiSuccessResponse();
+      await act(true);
+    });
+    testFn(`API responds with an error: ${failTestDescription ?? testDescription}`, async function() {
+      configureUid2ApiFailResponse();
+      await act(false);
+    });
+  }
+
   const getFullTestTitle = (test) => `${test.parent.title ? getFullTestTitle(test.parent) + ' | ' : ''}${test.title}`;
+
   beforeEach(function () {
     debugOutput(`----------------- START TEST ------------------`);
     fullTestTitle = getFullTestTitle(this.test.ctx.currentTest);
     debugOutput(fullTestTitle);
     testSandbox = sinon.sandbox.create();
     testSandbox.stub(utils, 'logWarn');
+    server = sinon.createFakeServer();
 
     init(config);
     setSubmoduleRegistry([uid2IdSubmodule]);
@@ -143,7 +144,6 @@ describe(`UID2 module`, function () {
     }
     cookieHelpers.clearCookies(moduleCookieName, publisherCookieName);
     coreStorage.removeDataFromLocalStorage(moduleCookieName);
-
     debugOutput('----------------- END TEST ------------------');
   });
 
@@ -247,7 +247,7 @@ describe(`UID2 module`, function () {
         describe('When the refresh is available in time', function() {
           testApiSuccessAndFailure(async function(apiSucceeds) {
             scenario.setConfig(apiHelpers.makeTokenResponse(initialToken, true, true));
-            apiHelpers.respondAfterDelay(auctionDelayMs / 10);
+            apiHelpers.respondAfterDelay(auctionDelayMs / 10, server);
             const bid = await runAuction();
 
             if (apiSucceeds) expectToken(bid, refreshedToken);
@@ -256,7 +256,7 @@ describe(`UID2 module`, function () {
 
           testApiSuccessAndFailure(async function(apiSucceeds) {
             scenario.setConfig(apiHelpers.makeTokenResponse(initialToken, true, true));
-            apiHelpers.respondAfterDelay(auctionDelayMs / 10);
+            apiHelpers.respondAfterDelay(auctionDelayMs / 10, server);
 
             await runAuction();
             if (apiSucceeds) {
@@ -275,7 +275,7 @@ describe(`UID2 module`, function () {
 
           testApiSuccessAndFailure(async function(apiSucceeds) {
             scenario.setConfig(apiHelpers.makeTokenResponse(initialToken, true, true));
-            const promise = apiHelpers.respondAfterDelay(auctionDelayMs * 2);
+            const promise = apiHelpers.respondAfterDelay(auctionDelayMs * 2, server);
 
             const bid = await runAuction();
             expectNoIdentity(bid);
@@ -319,13 +319,13 @@ describe(`UID2 module`, function () {
           scenario.setConfig(apiHelpers.makeTokenResponse(initialToken, true), {auctionDelay: 0, syncDelay: 1});
         });
         testApiSuccessAndFailure(async function() {
-          apiHelpers.respondAfterDelay(10);
+          apiHelpers.respondAfterDelay(10, server);
           const bid = await runAuction();
           expectToken(bid, initialToken);
         }, 'it should not be refreshed before the auction runs');
 
         testApiSuccessAndFailure(async function(success) {
-          const promise = apiHelpers.respondAfterDelay(1);
+          const promise = apiHelpers.respondAfterDelay(1, server);
           await runAuction();
           await promise;
           if (success) {
diff --git a/test/spec/modules/userId_spec.js b/test/spec/modules/userId_spec.js
index acc016a903d..68e42310c33 100644
--- a/test/spec/modules/userId_spec.js
+++ b/test/spec/modules/userId_spec.js
@@ -3005,7 +3005,7 @@ describe('User ID', function () {
           expect(server.requests).to.be.empty;
           return endAuction();
         }).then(() => {
-          expect(server.requests[0].url).to.equal('/any/unifiedid/url');
+          expect(server.requests[0].url).to.match(/\/any\/unifiedid\/url/);
         });
       });
 
diff --git a/test/spec/modules/zeta_global_sspAnalyticsAdapter_spec.js b/test/spec/modules/zeta_global_sspAnalyticsAdapter_spec.js
index 15a1155f378..cbba815cfc1 100644
--- a/test/spec/modules/zeta_global_sspAnalyticsAdapter_spec.js
+++ b/test/spec/modules/zeta_global_sspAnalyticsAdapter_spec.js
@@ -1,7 +1,7 @@
 import zetaAnalyticsAdapter from 'modules/zeta_global_sspAnalyticsAdapter.js';
 import {config} from 'src/config';
 import CONSTANTS from 'src/constants.json';
-import {logError} from '../../../src/utils';
+import {server} from '../../mocks/xhr.js';
 
 let utils = require('src/utils');
 let events = require('src/events');
@@ -358,14 +358,11 @@ const MOCK = {
 
 describe('Zeta Global SSP Analytics Adapter', function() {
   let sandbox;
-  let xhr;
   let requests;
 
   beforeEach(function() {
     sandbox = sinon.sandbox.create();
-    requests = [];
-    xhr = sandbox.useFakeXMLHttpRequest();
-    xhr.onCreate = request => requests.push(request);
+    requests = server.requests;
     sandbox.stub(events, 'getEvents').returns([]);
   });
 
diff --git a/test/spec/unit/core/ajax_spec.js b/test/spec/unit/core/ajax_spec.js
new file mode 100644
index 00000000000..df0ce02c15c
--- /dev/null
+++ b/test/spec/unit/core/ajax_spec.js
@@ -0,0 +1,403 @@
+import {dep, attachCallbacks, fetcherFactory, toFetchRequest} from '../../../../src/ajax.js';
+import {config} from 'src/config.js';
+import {server} from '../../../mocks/xhr.js';
+import {sandbox} from 'sinon';
+
+const EXAMPLE_URL = 'https://www.example.com';
+
+describe('fetcherFactory', () => {
+  let clock;
+
+  beforeEach(() => {
+    clock = sinon.useFakeTimers();
+    server.autoTimeout = true;
+  });
+
+  afterEach(() => {
+    clock.runAll();
+    clock.restore();
+    config.resetConfig();
+  });
+
+  Object.entries({
+    'URL': EXAMPLE_URL,
+    'request object': new Request(EXAMPLE_URL)
+  }).forEach(([t, resource]) => {
+    it(`times out after timeout when fetching ${t}`, (done) => {
+      const fetch = fetcherFactory(1000);
+      const resp = fetch(resource);
+      clock.tick(900);
+      expect(server.requests[0].fetch.request.signal.aborted).to.be.false;
+      clock.tick(100);
+      expect(server.requests[0].fetch.request.signal.aborted).to.be.true;
+      resp.catch(() => done());
+    });
+  });
+
+  it('does not timeout after it completes', () => {
+    const fetch = fetcherFactory(1000);
+    const resp = fetch(EXAMPLE_URL);
+    server.requests[0].respond();
+    return resp.then(() => {
+      clock.tick(2000);
+      expect(server.requests[0].fetch.request.signal.aborted).to.be.false;
+    });
+  });
+
+  Object.entries({
+    'disableAjaxTimeout is set'() {
+      const fetcher = fetcherFactory(1000);
+      config.setConfig({disableAjaxTimeout: true});
+      return fetcher;
+    },
+    'timeout is null'() {
+      return fetcherFactory(null);
+    },
+  }).forEach(([t, mkFetcher]) => {
+    it(`does not timeout if ${t}`, (done) => {
+      const fetch = mkFetcher();
+      const pm = fetch(EXAMPLE_URL);
+      clock.tick(2000);
+      server.requests[0].respond();
+      pm.then(() => done());
+    });
+  });
+
+  Object.entries({
+    'local URL': ['/local.html', window.origin],
+    'remote URL': [EXAMPLE_URL + '/remote.html', EXAMPLE_URL],
+    'request with local URL': [new Request('/local.html'), window.origin],
+    'request with remote URL': [new Request(EXAMPLE_URL + '/remote.html'), EXAMPLE_URL]
+  }).forEach(([t, [resource, expectedOrigin]]) => {
+    describe(`using ${t}`, () => {
+      it('calls request, passing origin', () => {
+        const request = sinon.stub();
+        const fetch = fetcherFactory(1000, {request});
+        fetch(resource);
+        sinon.assert.calledWith(request, expectedOrigin);
+      });
+
+      Object.entries({
+        success: 'respond',
+        error: 'error'
+      }).forEach(([t, method]) => {
+        it(`calls done on ${t}, passing origin`, () => {
+          const done = sinon.stub();
+          const fetch = fetcherFactory(1000, {done});
+          const req = fetch(resource).catch(() => null).then(() => {
+            sinon.assert.calledWith(done, expectedOrigin);
+          });
+          server.requests[0][method]();
+          return req;
+        });
+      });
+    });
+  });
+});
+
+describe('toFetchRequest', () => {
+  Object.entries({
+    'simple POST': {
+      url: EXAMPLE_URL,
+      data: 'data',
+      expect: {
+        request: {
+          url: EXAMPLE_URL + '/',
+          method: 'POST',
+        },
+        text: 'data',
+        headers: {
+          'content-type': 'text/plain'
+        }
+      }
+    },
+    'POST with headers': {
+      url: EXAMPLE_URL,
+      data: '{"json": "body"}',
+      options: {
+        contentType: 'application/json',
+        customHeaders: {
+          'x-custom': 'value'
+        }
+      },
+      expect: {
+        request: {
+          url: EXAMPLE_URL + '/',
+          method: 'POST',
+        },
+        text: '{"json": "body"}',
+        headers: {
+          'content-type': 'application/json',
+          'X-Custom': 'value'
+        }
+      }
+    },
+    'simple GET': {
+      url: EXAMPLE_URL,
+      data: {p1: 'v1', p2: 'v2'},
+      options: {
+        method: 'GET',
+      },
+      expect: {
+        request: {
+          url: EXAMPLE_URL + '/?p1=v1&p2=v2',
+          method: 'GET'
+        },
+        text: '',
+        headers: {
+          'content-type': 'text/plain'
+        }
+      }
+    },
+    'GET with credentials': {
+      url: EXAMPLE_URL,
+      data: null,
+      options: {
+        method: 'GET',
+        withCredentials: true,
+      },
+      expect: {
+        request: {
+          url: EXAMPLE_URL + '/',
+          method: 'GET',
+          credentials: 'include'
+        },
+        text: '',
+        headers: {
+          'content-type': 'text/plain'
+        }
+      }
+    }
+  }).forEach(([t, {url, data, options, expect: {request, text, headers}}]) => {
+    it(`can build ${t}`, () => {
+      const req = toFetchRequest(url, data, options);
+      return req.text().then(body => {
+        Object.entries(request).forEach(([prop, val]) => {
+          expect(req[prop]).to.eql(val);
+        });
+        const hdr = new Headers(headers);
+        Array.from(req.headers.entries()).forEach(([name, val]) => {
+          expect(hdr.get(name)).to.eql(val);
+        });
+        expect(body).to.eql(text);
+      });
+    });
+  });
+
+  describe('browsingTopics', () => {
+    Object.entries({
+      'browsingTopics = true': [{browsingTopics: true}, true],
+      'browsingTopics = false': [{browsingTopics: false}, false],
+      'browsingTopics is undef': [{}, false]
+    }).forEach(([t, [opts, shouldBeSet]]) => {
+      describe(`when options has ${t}`, () => {
+        const sandbox = sinon.createSandbox();
+        afterEach(() => {
+          sandbox.restore();
+        });
+
+        it(`should ${!shouldBeSet ? 'not ' : ''}be set when in a secure context`, () => {
+          sandbox.stub(window, 'isSecureContext').get(() => true);
+          toFetchRequest(EXAMPLE_URL, null, opts);
+          sinon.assert.calledWithMatch(dep.makeRequest, sinon.match.any, {browsingTopics: shouldBeSet ? true : undefined});
+        });
+        it(`should not be set when not in a secure context`, () => {
+          sandbox.stub(window, 'isSecureContext').get(() => false);
+          toFetchRequest(EXAMPLE_URL, null, opts);
+          sinon.assert.calledWithMatch(dep.makeRequest, sinon.match.any, {browsingTopics: undefined});
+        });
+      })
+    })
+  })
+});
+
+describe('attachCallbacks', () => {
+  const sampleHeaders = new Headers({
+    'x-1': 'v1',
+    'x-2': 'v2'
+  });
+
+  function responseFactory(body, props) {
+    props = Object.assign({headers: sampleHeaders, url: EXAMPLE_URL}, props);
+    return function () {
+      return {
+        response: Object.defineProperties(new Response(body, props), {
+          url: {
+            get: () => props.url
+          }
+        }),
+        body: body || ''
+      };
+    };
+  }
+
+  function expectNullXHR(response) {
+    return new Promise((resolve, reject) => {
+      attachCallbacks(Promise.resolve(response), {
+        success: () => {
+          reject(new Error('should not succeed'));
+        },
+        error(statusText, xhr) {
+          expect(statusText).to.eql('');
+          sinon.assert.match(xhr, {
+            readyState: XMLHttpRequest.DONE,
+            status: 0,
+            statusText: '',
+            responseText: '',
+            response: '',
+            responseXML: null
+          });
+          expect(xhr.getResponseHeader('any')).to.be.null;
+          resolve();
+        }
+      });
+    });
+  }
+
+  it('runs error callback on rejections', () => {
+    return expectNullXHR(Promise.reject(new Error()));
+  });
+
+  Object.entries({
+    '2xx response': {
+      success: true,
+      makeResponse: responseFactory('body', {status: 200, statusText: 'OK'})
+    },
+    '2xx response with no body': {
+      success: true,
+      makeResponse: responseFactory(null, {status: 204, statusText: 'No content'})
+    },
+    '2xx response with XML': {
+      success: true,
+      xml: true,
+      makeResponse: responseFactory('<?xml><root><tag /></root>', {
+        status: 200,
+        statusText: 'OK',
+        headers: {'content-type': 'application/xml;charset=UTF8'}
+      })
+    },
+    '2xx response with HTML': {
+      success: true,
+      xml: true,
+      makeResponse: responseFactory('<html lang="en"><p></p></html>', {
+        status: 200,
+        statusText: 'OK',
+        headers: {'content-type': 'text/html;charset=UTF-8'}
+      })
+    },
+    '304 response': {
+      success: true,
+      makeResponse: responseFactory(null, {status: 304, statusText: 'Moved permanently'})
+    },
+    '4xx response': {
+      success: false,
+      makeResponse: responseFactory('body', {status: 400, statusText: 'Invalid request'})
+    },
+    '5xx response': {
+      success: false,
+      makeResponse: responseFactory('body', {status: 503, statusText: 'Gateway error'})
+    },
+    '4xx response with XML': {
+      success: false,
+      xml: true,
+      makeResponse: responseFactory('<?xml><root></root>', {
+        status: 404,
+        statusText: 'Not found',
+        headers: {
+          'content-type': 'application/xml'
+        }
+      })
+    }
+  }).forEach(([t, {success, makeResponse, xml}]) => {
+    const cbType = success ? 'success' : 'error';
+
+    describe(`for ${t}`, () => {
+      let response, body;
+      beforeEach(() => {
+        ({response, body} = makeResponse());
+      });
+
+      function checkXHR(xhr) {
+        sinon.assert.match(xhr, {
+          readyState: XMLHttpRequest.DONE,
+          status: response.status,
+          statusText: response.statusText,
+          responseType: '',
+          responseURL: response.url,
+          response: body,
+          responseText: body,
+        });
+        if (xml) {
+          expect(xhr.responseXML.querySelectorAll('*').length > 0).to.be.true;
+        } else {
+          expect(xhr.responseXML).to.not.exist;
+        }
+        Array.from(response.headers.entries()).forEach(([name, value]) => {
+          expect(xhr.getResponseHeader(name)).to.eql(value);
+        });
+        expect(xhr.getResponseHeader('$$missing-header')).to.be.null;
+      }
+
+      it(`runs ${cbType} callback`, (done) => {
+        attachCallbacks(Promise.resolve(response), {
+          success(payload, xhr) {
+            expect(success).to.be.true;
+            expect(payload).to.eql(body);
+            checkXHR(xhr);
+            done();
+          },
+          error(statusText, xhr) {
+            expect(success).to.be.false;
+            expect(statusText).to.eql(response.statusText);
+            checkXHR(xhr);
+            done();
+          }
+        });
+      });
+
+      it(`runs error callback if body cannot be retrieved`, () => {
+        response.text = () => Promise.reject(new Error());
+        return expectNullXHR(response);
+      });
+
+      if (success) {
+        it('accepts a single function as success callback', (done) => {
+          attachCallbacks(Promise.resolve(response), function (payload, xhr) {
+            expect(payload).to.eql(body);
+            checkXHR(xhr);
+            done();
+          })
+        })
+      }
+    });
+  });
+
+  describe('callback exceptions', () => {
+    Object.entries({
+      success: responseFactory(null, {status: 204}),
+      error: responseFactory('', {status: 400}),
+    }).forEach(([cbType, makeResponse]) => {
+      it(`do not choke ${cbType} callbacks`, () => {
+        const {response} = makeResponse();
+        return new Promise((resolve) => {
+          const result = {success: false, error: false};
+          attachCallbacks(Promise.resolve(response), {
+            success() {
+              result.success = true;
+              throw new Error();
+            },
+            error() {
+              result.error = true;
+              throw new Error();
+            }
+          });
+          setTimeout(() => resolve(result), 20);
+        }).then(result => {
+          Object.entries(result).forEach(([typ, ran]) => {
+            expect(ran).to.be[typ === cbType ? 'true' : 'false']
+          })
+        });
+      });
+    });
+  });
+});
diff --git a/test/spec/unit/core/bidderFactory_spec.js b/test/spec/unit/core/bidderFactory_spec.js
index 138ffcb608d..0360679ca52 100644
--- a/test/spec/unit/core/bidderFactory_spec.js
+++ b/test/spec/unit/core/bidderFactory_spec.js
@@ -14,7 +14,7 @@ import {bidderSettings} from '../../../../src/bidderSettings.js';
 import {decorateAdUnitsWithNativeParams} from '../../../../src/native.js';
 import * as activityRules from 'src/activities/rules.js';
 import {MODULE_TYPE_BIDDER} from '../../../../src/activities/modules.js';
-import {ACTIVITY_TRANSMIT_TID} from '../../../../src/activities/activities.js';
+import {ACTIVITY_TRANSMIT_TID, ACTIVITY_TRANSMIT_UFPD} from '../../../../src/activities/activities.js';
 
 const CODE = 'sampleBidder';
 const MOCK_BIDS_REQUEST = {
@@ -319,7 +319,7 @@ describe('bidders created by newBidder', function () {
       expect(ajaxStub.calledOnce).to.equal(true);
       expect(ajaxStub.firstCall.args[0]).to.equal(url);
       expect(ajaxStub.firstCall.args[2]).to.equal(JSON.stringify(data));
-      expect(ajaxStub.firstCall.args[3]).to.deep.equal({
+      sinon.assert.match(ajaxStub.firstCall.args[3], {
         method: 'POST',
         contentType: 'text/plain',
         withCredentials: true
@@ -344,11 +344,11 @@ describe('bidders created by newBidder', function () {
       expect(ajaxStub.calledOnce).to.equal(true);
       expect(ajaxStub.firstCall.args[0]).to.equal(url);
       expect(ajaxStub.firstCall.args[2]).to.equal(JSON.stringify(data));
-      expect(ajaxStub.firstCall.args[3]).to.deep.equal({
+      sinon.assert.match(ajaxStub.firstCall.args[3], {
         method: 'POST',
         contentType: 'application/json',
         withCredentials: true
-      });
+      })
     });
 
     it('should make the appropriate GET request', function () {
@@ -367,10 +367,10 @@ describe('bidders created by newBidder', function () {
       expect(ajaxStub.calledOnce).to.equal(true);
       expect(ajaxStub.firstCall.args[0]).to.equal(`${url}?arg=2`);
       expect(ajaxStub.firstCall.args[2]).to.be.undefined;
-      expect(ajaxStub.firstCall.args[3]).to.deep.equal({
+      sinon.assert.match(ajaxStub.firstCall.args[3], {
         method: 'GET',
         withCredentials: true
-      });
+      })
     });
 
     it('should make the appropriate GET request when options are passed', function () {
@@ -391,10 +391,10 @@ describe('bidders created by newBidder', function () {
       expect(ajaxStub.calledOnce).to.equal(true);
       expect(ajaxStub.firstCall.args[0]).to.equal(`${url}?arg=2`);
       expect(ajaxStub.firstCall.args[2]).to.be.undefined;
-      expect(ajaxStub.firstCall.args[3]).to.deep.equal({
+      sinon.assert.match(ajaxStub.firstCall.args[3], {
         method: 'GET',
         withCredentials: false
-      });
+      })
     });
 
     it('should make multiple calls if the spec returns them', function () {
@@ -420,6 +420,78 @@ describe('bidders created by newBidder', function () {
       expect(ajaxStub.calledTwice).to.equal(true);
     });
 
+    describe('browsingTopics ajax option', () => {
+      let transmitUfpdAllowed, bidder;
+      beforeEach(() => {
+        activityRules.isActivityAllowed.reset();
+        activityRules.isActivityAllowed.callsFake((activity) => activity === ACTIVITY_TRANSMIT_UFPD ? transmitUfpdAllowed : true);
+        bidder = newBidder(spec);
+        spec.isBidRequestValid.returns(true);
+      });
+
+      it(`should be set to false when adapter sets browsingTopics = false`, () => {
+        transmitUfpdAllowed = true;
+        spec.buildRequests.returns([
+          {
+            method: 'GET',
+            url: 'url',
+            options: {
+              browsingTopics: false
+            }
+          }
+        ]);
+        bidder.callBids(MOCK_BIDS_REQUEST, addBidResponseStub, doneStub, ajaxStub, onTimelyResponseStub, wrappedCallback);
+        sinon.assert.calledWith(ajaxStub, 'url', sinon.match.any, sinon.match.any, sinon.match({
+          browsingTopics: false
+        }));
+      });
+
+      Object.entries({
+        'allowed': true,
+        'not allowed': false
+      }).forEach(([t, allow]) => {
+        it(`should be set to ${allow} when transmitUfpd is ${t}`, () => {
+          transmitUfpdAllowed = allow;
+          spec.buildRequests.returns([
+            {
+              method: 'GET',
+              url: '1',
+            },
+            {
+              method: 'POST',
+              url: '2',
+              data: {}
+            },
+            {
+              method: 'GET',
+              url: '3',
+              options: {
+                browsingTopics: true
+              }
+            },
+            {
+              method: 'POST',
+              url: '4',
+              data: {},
+              options: {
+                browsingTopics: true
+              }
+            }
+          ]);
+          bidder.callBids(MOCK_BIDS_REQUEST, addBidResponseStub, doneStub, ajaxStub, onTimelyResponseStub, wrappedCallback);
+          ['1', '2', '3', '4'].forEach(url => {
+            sinon.assert.calledWith(
+              ajaxStub,
+              url,
+              sinon.match.any,
+              sinon.match.any,
+              sinon.match({browsingTopics: allow})
+            );
+          });
+        });
+      });
+    });
+
     it('should not add bids for each placement code if no requests are given', function () {
       const bidder = newBidder(spec);
 
diff --git a/test/spec/videoCache_spec.js b/test/spec/videoCache_spec.js
index c7c0b2eb329..c746fdd2afd 100644
--- a/test/spec/videoCache_spec.js
+++ b/test/spec/videoCache_spec.js
@@ -174,7 +174,7 @@ describe('The video cache', function () {
       const request = server.requests[0];
       request.method.should.equal('POST');
       request.url.should.equal('https://prebid.adnxs.com/pbc/v1/cache');
-      request.requestHeaders['Content-Type'].should.equal('text/plain;charset=utf-8');
+      request.requestHeaders['Content-Type'].should.equal('text/plain');
       let payload = {
         puts: [{
           type: 'xml',
@@ -224,7 +224,7 @@ describe('The video cache', function () {
       const request = server.requests[0];
       request.method.should.equal('POST');
       request.url.should.equal('https://prebid.adnxs.com/pbc/v1/cache');
-      request.requestHeaders['Content-Type'].should.equal('text/plain;charset=utf-8');
+      request.requestHeaders['Content-Type'].should.equal('text/plain');
       let payload = {
         puts: [{
           type: 'xml',
@@ -295,7 +295,7 @@ describe('The video cache', function () {
       const request = server.requests[0];
       request.method.should.equal('POST');
       request.url.should.equal('https://prebid.adnxs.com/pbc/v1/cache');
-      request.requestHeaders['Content-Type'].should.equal('text/plain;charset=utf-8');
+      request.requestHeaders['Content-Type'].should.equal('text/plain');
       let payload = {
         puts: [{
           type: 'xml',
@@ -356,7 +356,7 @@ describe('The video cache', function () {
       const request = server.requests[0];
       request.method.should.equal('POST');
       request.url.should.equal('https://prebid.adnxs.com/pbc/v1/cache');
-      request.requestHeaders['Content-Type'].should.equal('text/plain;charset=utf-8');
+      request.requestHeaders['Content-Type'].should.equal('text/plain');
 
       JSON.parse(request.requestBody).should.deep.equal({
         puts: [{