diff --git a/packages/docusaurus-module-type-aliases/src/index.d.ts b/packages/docusaurus-module-type-aliases/src/index.d.ts
index ae41e1d54c3e..306c41e37393 100644
--- a/packages/docusaurus-module-type-aliases/src/index.d.ts
+++ b/packages/docusaurus-module-type-aliases/src/index.d.ts
@@ -37,6 +37,29 @@ declare module '@generated/routesChunkNames' {
   export default routesChunkNames;
 }
 
+declare module '@generated/site-metadata' {
+  /**
+   * - `type: 'package'`, plugin is in a different package.
+   * - `type: 'project'`, plugin is in the same docusaurus project.
+   * - `type: 'local'`, none of plugin's ancestor directory contains any package.json.
+   * - `type: 'synthetic'`, docusaurus generated internal plugin.
+   */
+  export type PluginVersionInformation =
+    | {readonly type: 'package'; readonly version?: string}
+    | {readonly type: 'project'}
+    | {readonly type: 'local'}
+    | {readonly type: 'synthetic'};
+
+  export type DocusaurusSiteMetadata = {
+    readonly docusaurusVersion: string;
+    readonly siteVersion?: string;
+    readonly pluginVersions: Record<string, PluginVersionInformation>;
+  };
+
+  const siteMetadata: DocusaurusSiteMetadata;
+  export default siteMetadata;
+}
+
 declare module '@theme/*';
 
 declare module '@theme-original/*';
diff --git a/packages/docusaurus-plugin-debug/src/theme/Debug/index.js b/packages/docusaurus-plugin-debug/src/theme/Debug/index.js
index 74446ae2e5f3..1dc44d973a53 100644
--- a/packages/docusaurus-plugin-debug/src/theme/Debug/index.js
+++ b/packages/docusaurus-plugin-debug/src/theme/Debug/index.js
@@ -10,6 +10,7 @@ import Layout from '@theme/Layout';
 
 import registry from '@generated/registry';
 import routes from '@generated/routes';
+import siteMetadata from '@generated/site-metadata';
 
 import styles from './styles.module.css';
 
@@ -17,7 +18,28 @@ function Debug() {
   return (
     <Layout permalink="__docusaurus/debug" title="Debug">
       <main className={styles.Container}>
-        <section>
+        <section className={styles.Section}>
+          <h2>Site Metadata</h2>
+          <div>Docusaurus Version: {siteMetadata.docusaurusVersion}</div>
+          <div>
+            Site Version: {siteMetadata.siteVersion || 'No version specified'}
+          </div>
+          <h3>Plugins and themes:</h3>
+          <ul>
+            {Object.entries(siteMetadata.pluginVersions).map(
+              ([name, versionInformation]) => (
+                <li key={name}>
+                  <div>Name: {name}</div>
+                  <div>Type: {versionInformation.type}</div>
+                  {versionInformation.version && (
+                    <div>Version: {versionInformation.version}</div>
+                  )}
+                </li>
+              ),
+            )}
+          </ul>
+        </section>
+        <section className={styles.Section}>
           <h2>Registry</h2>
           <ul>
             {Object.values(registry).map(([, aliasedPath, resolved]) => (
@@ -28,7 +50,7 @@ function Debug() {
             ))}
           </ul>
         </section>
-        <section>
+        <section className={styles.Section}>
           <h2>Routes</h2>
           <ul>
             {routes.map(({path, exact}) => (
diff --git a/packages/docusaurus-plugin-debug/src/theme/Debug/styles.module.css b/packages/docusaurus-plugin-debug/src/theme/Debug/styles.module.css
index cb621a15abf8..8dee72f3c8ac 100644
--- a/packages/docusaurus-plugin-debug/src/theme/Debug/styles.module.css
+++ b/packages/docusaurus-plugin-debug/src/theme/Debug/styles.module.css
@@ -7,5 +7,11 @@
 
 .Container {
   display: flex;
+  flex-wrap: wrap;
+  justify-content: center;
   margin: 1em;
 }
+
+.Section {
+  width: 500px;
+}
diff --git a/packages/docusaurus/src/server/index.ts b/packages/docusaurus/src/server/index.ts
index 8d89c1edc817..c1d729027354 100644
--- a/packages/docusaurus/src/server/index.ts
+++ b/packages/docusaurus/src/server/index.ts
@@ -6,7 +6,8 @@
  */
 
 import {generate} from '@docusaurus/utils';
-import path from 'path';
+import {DocusaurusSiteMetadata} from '@generated/site-metadata';
+import path, {join} from 'path';
 import {
   BUILD_DIR_NAME,
   CONFIG_FILE_NAME,
@@ -26,6 +27,7 @@ import {
   Props,
 } from '@docusaurus/types';
 import {loadHtmlTags} from './html-tags';
+import {getPackageJsonVersion} from './versions';
 
 export function loadContext(
   siteDir: string,
@@ -96,6 +98,7 @@ export async function load(
   const {stylesheets = [], scripts = []} = siteConfig;
   plugins.push({
     name: 'docusaurus-bootstrap-plugin',
+    version: {type: 'synthetic'},
     configureWebpack: () => ({
       resolve: {
         alias,
@@ -178,12 +181,32 @@ ${Object.keys(registry)
 
   const genRoutes = generate(generatedFilesDir, 'routes.js', routesConfig);
 
+  // Version metadata.
+  const siteMetadata: DocusaurusSiteMetadata = {
+    docusaurusVersion: getPackageJsonVersion(
+      join(__dirname, '../../package.json'),
+    )!,
+    siteVersion: getPackageJsonVersion(join(siteDir, 'package.json')),
+    pluginVersions: {},
+  };
+  plugins
+    .filter(({version: {type}}) => type !== 'synthetic')
+    .forEach(({name, version}) => {
+      siteMetadata.pluginVersions[name] = version;
+    });
+  const genSiteMetadata = generate(
+    generatedFilesDir,
+    'site-metadata.json',
+    JSON.stringify(siteMetadata, null, 2),
+  );
+
   await Promise.all([
     genClientModules,
     genSiteConfig,
     genRegistry,
     genRoutesChunkNames,
     genRoutes,
+    genSiteMetadata,
   ]);
 
   const props: Props = {
diff --git a/packages/docusaurus/src/server/plugins/index.ts b/packages/docusaurus/src/server/plugins/index.ts
index 100d28d4cda6..3657b2be7409 100644
--- a/packages/docusaurus/src/server/plugins/index.ts
+++ b/packages/docusaurus/src/server/plugins/index.ts
@@ -10,12 +10,11 @@ import fs from 'fs-extra';
 import path from 'path';
 import {
   LoadContext,
-  Plugin,
   PluginConfig,
   PluginContentLoadedActions,
   RouteConfig,
 } from '@docusaurus/types';
-import initPlugins from './init';
+import initPlugins, {PluginWithVersionInformation} from './init';
 
 export function sortConfig(routeConfigs: RouteConfig[]): void {
   // Sort the route config. This ensures that route with nested
@@ -53,11 +52,14 @@ export async function loadPlugins({
   pluginConfigs: PluginConfig[];
   context: LoadContext;
 }): Promise<{
-  plugins: Plugin<unknown>[];
+  plugins: PluginWithVersionInformation[];
   pluginsRouteConfigs: RouteConfig[];
 }> {
   // 1. Plugin Lifecycle - Initialization/Constructor.
-  const plugins: Plugin<unknown>[] = initPlugins({pluginConfigs, context});
+  const plugins: PluginWithVersionInformation[] = initPlugins({
+    pluginConfigs,
+    context,
+  });
 
   // 2. Plugin Lifecycle - loadContent.
   // Currently plugins run lifecycle methods in parallel and are not order-dependent.
diff --git a/packages/docusaurus/src/server/plugins/init.ts b/packages/docusaurus/src/server/plugins/init.ts
index 11b0fee25524..93a8fcb67ae9 100644
--- a/packages/docusaurus/src/server/plugins/init.ts
+++ b/packages/docusaurus/src/server/plugins/init.ts
@@ -14,7 +14,9 @@ import {
   PluginConfig,
   ValidationSchema,
 } from '@docusaurus/types';
+import {PluginVersionInformation} from '@generated/site-metadata';
 import {CONFIG_FILE_NAME} from '../../constants';
+import {getPluginVersion} from '../versions';
 
 function validate<T>(schema: ValidationSchema<T>, options: Partial<T>) {
   const {error, value} = schema.validate(options, {
@@ -37,13 +39,17 @@ function validateAndStrip<T>(schema: ValidationSchema<T>, options: Partial<T>) {
   return value;
 }
 
+export type PluginWithVersionInformation = Plugin<unknown> & {
+  readonly version: PluginVersionInformation;
+};
+
 export default function initPlugins({
   pluginConfigs,
   context,
 }: {
   pluginConfigs: PluginConfig[];
   context: LoadContext;
-}): Plugin<unknown>[] {
+}): PluginWithVersionInformation[] {
   // We need to resolve plugins from the perspective of the siteDir, since the siteDir's package.json
   // declares the dependency on these plugins.
   // We need to fallback to createRequireFromPath since createRequire is only available in node v12.
@@ -51,7 +57,7 @@ export default function initPlugins({
   const createRequire = Module.createRequire || Module.createRequireFromPath;
   const pluginRequire = createRequire(join(context.siteDir, CONFIG_FILE_NAME));
 
-  const plugins: Plugin<unknown>[] = pluginConfigs
+  const plugins: PluginWithVersionInformation[] = pluginConfigs
     .map((pluginItem) => {
       let pluginModuleImport: string | undefined;
       let pluginOptions = {};
@@ -72,9 +78,9 @@ export default function initPlugins({
 
       // The pluginModuleImport value is any valid
       // module identifier - npm package or locally-resolved path.
-      const pluginModule: any = importFresh(
-        pluginRequire.resolve(pluginModuleImport),
-      );
+      const pluginPath = pluginRequire.resolve(pluginModuleImport);
+      const pluginModule: any = importFresh(pluginPath);
+      const pluginVersion = getPluginVersion(pluginPath, context.siteDir);
 
       const plugin = pluginModule.default || pluginModule;
 
@@ -106,7 +112,7 @@ export default function initPlugins({
           ...normalizedThemeConfig,
         };
       }
-      return plugin(context, pluginOptions);
+      return {...plugin(context, pluginOptions), version: pluginVersion};
     })
     .filter(Boolean);
   return plugins;
diff --git a/packages/docusaurus/src/server/types.d.ts b/packages/docusaurus/src/server/types.d.ts
new file mode 100644
index 000000000000..37777ca928d7
--- /dev/null
+++ b/packages/docusaurus/src/server/types.d.ts
@@ -0,0 +1,11 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// triple slash is important to keep,
+// see https://www.typescriptlang.org/docs/handbook/triple-slash-directives.html
+// eslint-disable-next-line
+/// <reference types="@docusaurus/module-type-aliases" />
diff --git a/packages/docusaurus/src/server/versions/__fixtures__/dummy-plugin.js b/packages/docusaurus/src/server/versions/__fixtures__/dummy-plugin.js
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/docusaurus/src/server/versions/__fixtures__/package.json b/packages/docusaurus/src/server/versions/__fixtures__/package.json
new file mode 100644
index 000000000000..531c8b2b61d9
--- /dev/null
+++ b/packages/docusaurus/src/server/versions/__fixtures__/package.json
@@ -0,0 +1,3 @@
+{
+  "version": "random-version"
+}
diff --git a/packages/docusaurus/src/server/versions/__tests/index.test.ts b/packages/docusaurus/src/server/versions/__tests/index.test.ts
new file mode 100644
index 000000000000..d2eb6370eb19
--- /dev/null
+++ b/packages/docusaurus/src/server/versions/__tests/index.test.ts
@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {getPluginVersion} from '..';
+import {join} from 'path';
+
+describe('getPluginVersion', () => {
+  it('Can detect external packages plugins versions of correctly.', () => {
+    expect(
+      getPluginVersion(
+        join(__dirname, '..', '__fixtures__', 'dummy-plugin.js'),
+        // Make the plugin appear external.
+        join(__dirname, '..', '..', '..', '..', '..', '..', 'website'),
+      ),
+    ).toEqual({type: 'package', version: 'random-version'});
+  });
+
+  it('Can detect project plugins versions correctly.', () => {
+    expect(
+      getPluginVersion(
+        join(__dirname, '..', '__fixtures__', 'dummy-plugin.js'),
+        // Make the plugin appear project local.
+        join(__dirname, '..', '__fixtures__'),
+      ),
+    ).toEqual({type: 'project'});
+  });
+
+  it('Can detect local packages versions correctly.', () => {
+    expect(getPluginVersion('/', '/')).toEqual({type: 'local'});
+  });
+});
diff --git a/packages/docusaurus/src/server/versions/index.ts b/packages/docusaurus/src/server/versions/index.ts
new file mode 100644
index 000000000000..03114a171227
--- /dev/null
+++ b/packages/docusaurus/src/server/versions/index.ts
@@ -0,0 +1,49 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {PluginVersionInformation} from '@generated/site-metadata';
+import {existsSync, lstatSync} from 'fs-extra';
+import {dirname, join} from 'path';
+
+export function getPackageJsonVersion(
+  packageJsonPath: string,
+): string | undefined {
+  if (existsSync(packageJsonPath)) {
+    // eslint-disable-next-line @typescript-eslint/no-var-requires, import/no-dynamic-require, global-require
+    const {version} = require(packageJsonPath);
+    return typeof version === 'string' ? version : undefined;
+  }
+  return undefined;
+}
+
+export function getPluginVersion(
+  pluginPath: string,
+  siteDir: string,
+): PluginVersionInformation {
+  let potentialPluginPackageJsonDirectory = dirname(pluginPath);
+  while (potentialPluginPackageJsonDirectory !== '/') {
+    const packageJsonPath = join(
+      potentialPluginPackageJsonDirectory,
+      'package.json',
+    );
+    if (existsSync(packageJsonPath) && lstatSync(packageJsonPath).isFile()) {
+      if (potentialPluginPackageJsonDirectory === siteDir) {
+        // If the plugin belongs to the same docusaurus project, we classify it as local plugin.
+        return {type: 'project'};
+      }
+      return {
+        type: 'package',
+        version: getPackageJsonVersion(packageJsonPath),
+      };
+    }
+    potentialPluginPackageJsonDirectory = dirname(
+      potentialPluginPackageJsonDirectory,
+    );
+  }
+  // In rare cases where a plugin is a path where no parent directory contains package.json, we can only classify it as local.
+  return {type: 'local'};
+}