diff --git a/package.json b/package.json
index a4a0769..e819cc9 100644
--- a/package.json
+++ b/package.json
@@ -12,7 +12,7 @@
     "Testing"
   ],
   "activationEvents": [
-    "onLanguage:json"
+    "onStartupFinished"
   ],
   "repository": {
     "type": "git",
diff --git a/src/codelens.ts b/src/codelens.ts
index 5f10099..363bdc2 100644
--- a/src/codelens.ts
+++ b/src/codelens.ts
@@ -1,7 +1,16 @@
 import * as vscode from 'vscode';
-import {isConfigFile, getASTNode, getRangeFromASTNode} from './helpers';
+import { isConfigFile, getASTNode, getRangeFromASTNode } from './helpers';
 import parse from 'json-to-ast';
 
+export const registerCodeLens = (context: vscode.ExtensionContext) => {
+  context.subscriptions.push(
+    vscode.languages.registerCodeLensProvider(
+      { scheme: 'file', language: 'json' },
+      pluginLensProvider
+    )
+  );
+};
+
 export const pluginLensProvider: vscode.CodeLensProvider = {
   provideCodeLenses(
     document: vscode.TextDocument,
diff --git a/src/commands.ts b/src/commands.ts
new file mode 100644
index 0000000..c7dd8dc
--- /dev/null
+++ b/src/commands.ts
@@ -0,0 +1,20 @@
+import * as vscode from 'vscode';
+import { pluginDocs } from './constants';
+
+export const registerCommands = (context: vscode.ExtensionContext) => {
+    context.subscriptions.push(
+        vscode.commands.registerCommand('dev-proxy-toolkit.install', async (platform: NodeJS.Platform) => {
+            const url = `https://aka.ms/devproxy/install/${platform === 'darwin' ? 'macos' : 'windows'}`;
+            vscode.env.openExternal(vscode.Uri.parse(url));
+        }));
+
+    context.subscriptions.push(
+        vscode.commands.registerCommand(
+            'dev-proxy-toolkit.openPluginDoc',
+            pluginName => {
+                const target = vscode.Uri.parse(pluginDocs[pluginName].url);
+                vscode.env.openExternal(target);
+            }
+        )
+    );
+};
\ No newline at end of file
diff --git a/src/detect.ts b/src/detect.ts
new file mode 100644
index 0000000..91e069b
--- /dev/null
+++ b/src/detect.ts
@@ -0,0 +1,72 @@
+import { exec } from 'child_process';
+import { DevProxyInstall } from './types';
+import os from 'os';
+
+const getExecutablePath = async (filename: string): Promise<string> => {
+    const command = getFindCommand();
+    if (command === '') {
+        return '';
+    }
+
+    try {
+        return await executeCommand(`${command} ${filename}`);
+    } catch (error) {
+        console.error(error);
+        return '';
+    }
+};
+
+const getFindCommand = () => {
+    const platform = os.platform();
+    let command = '';
+    if (platform === 'win32') {
+        command = 'pwsh.exe -c "where.exe devproxy"';
+    }
+    if (platform === 'darwin') {
+        command = '$SHELL -c "which devproxy"';
+    }
+    return command;
+};
+
+const getVersion = async (filePath: string) => {
+    if (filePath === '') {
+        return '';
+    }
+    try {
+        const version = await executeCommand(`${filePath.trim()} --version`);
+        return version.trim();
+    } catch (error) {
+        console.error(error);
+        return "";
+    }
+};
+
+export const executeCommand = async (cmd: string): Promise<string> => {
+    return new Promise((resolve, reject) => {
+        exec(cmd, (error, stdout, stderr) => {
+            if (error) {
+                reject(`exec error: ${error}`);
+            } else if (stderr) {
+                reject(`stderr: ${stderr}`);
+            } else {
+                resolve(stdout);
+            }
+        });
+    });
+};
+
+export const detectDevProxyInstall = async (): Promise<DevProxyInstall> => {
+    const filePath = await getExecutablePath('devproxy');
+    const version = await getVersion(filePath);
+    const isInstalled = filePath !== '';
+    const isBeta = version.includes('beta');
+    const platform = os.platform();
+
+    return {
+        filePath,
+        version,
+        isInstalled,
+        isBeta,
+        platform
+    };
+};
\ No newline at end of file
diff --git a/src/diagnostics.ts b/src/diagnostics.ts
new file mode 100644
index 0000000..7e6cae4
--- /dev/null
+++ b/src/diagnostics.ts
@@ -0,0 +1,124 @@
+import * as vscode from 'vscode';
+import parse from "json-to-ast";
+import { pluginSnippets } from "./constants";
+import { getASTNode, getRangeFromASTNode } from "./helpers";
+
+export const updateDiagnostics = (
+    document: vscode.TextDocument,
+    collection: vscode.DiagnosticCollection
+  ): void => {
+    let diagnostics: vscode.Diagnostic[] = [];
+  
+    const documentNode = parse(document.getText()) as parse.ObjectNode;
+  
+    // check if urlsToWatch is empty
+    const urlsToWatchNode = getASTNode(
+      documentNode.children,
+      'Identifier',
+      'urlsToWatch'
+    );
+    if (
+      urlsToWatchNode &&
+      (urlsToWatchNode.value as parse.ArrayNode).children.length === 0
+    ) {
+      diagnostics.push(
+        new vscode.Diagnostic(
+          getRangeFromASTNode(urlsToWatchNode),
+          'Add at least one url to watch.',
+          vscode.DiagnosticSeverity.Error
+        )
+      );
+    }
+  
+    // check validity of plugins
+    const pluginsNode = getASTNode(
+      documentNode.children,
+      'Identifier',
+      'plugins'
+    );
+    if (
+      pluginsNode &&
+      (pluginsNode.value as parse.ArrayNode).children.length !== 0
+    ) {
+      const pluginNodes = (pluginsNode.value as parse.ArrayNode)
+        .children as parse.ObjectNode[];
+  
+      // check for plugins
+      if (pluginNodes.length === 0) {
+        diagnostics.push(
+          new vscode.Diagnostic(
+            getRangeFromASTNode(pluginsNode),
+            'Add at least one plugin',
+            vscode.DiagnosticSeverity.Error
+          )
+        );
+      }
+  
+      // does the plugin have a config section?
+      pluginNodes.forEach((pluginNode: parse.ObjectNode) => {
+        const pluginNameNode = getASTNode(
+          pluginNode.children,
+          'Identifier',
+          'name'
+        );
+        const pluginName = (pluginNameNode?.value as parse.LiteralNode)
+          .value as string;
+        const enabledNode = getASTNode(
+          pluginNode.children,
+          'Identifier',
+          'enabled'
+        );
+        const isEnabled = (enabledNode?.value as parse.LiteralNode)
+          .value as boolean;
+        const pluginSnippet = pluginSnippets[pluginName];
+        const requiresConfig = pluginSnippet.config
+          ? pluginSnippet.config.required
+          : false;
+  
+        if (requiresConfig) {
+          // check to see if the plugin has a config section
+          const configSectionNode = getASTNode(
+            pluginNode.children,
+            'Identifier',
+            'configSection'
+          );
+          if (!configSectionNode) {
+            // there is no config section defined on the plugin instance
+            diagnostics.push(
+              new vscode.Diagnostic(
+                getRangeFromASTNode(pluginNode),
+                `${pluginName} requires a config section.`,
+                isEnabled
+                  ? vscode.DiagnosticSeverity.Error
+                  : vscode.DiagnosticSeverity.Warning
+              )
+            );
+          } else {
+            // check to see if the config section is in the document
+            const configSectionName = (
+              configSectionNode.value as parse.LiteralNode
+            ).value as string;
+            const configSection = getASTNode(
+              documentNode.children,
+              'Identifier',
+              configSectionName
+            );
+  
+            if (!configSection) {
+              diagnostics.push(
+                new vscode.Diagnostic(
+                  getRangeFromASTNode(configSectionNode.value),
+                  `${configSectionName} config section is missing. Use '${pluginSnippet.config?.name}' snippet to create one.`,
+                  isEnabled
+                    ? vscode.DiagnosticSeverity.Error
+                    : vscode.DiagnosticSeverity.Warning
+                )
+              );
+            }
+          }
+        }
+      });
+    }
+  
+    collection.set(document.uri, diagnostics);
+  };
\ No newline at end of file
diff --git a/src/documents.ts b/src/documents.ts
new file mode 100644
index 0000000..96b4582
--- /dev/null
+++ b/src/documents.ts
@@ -0,0 +1,24 @@
+import * as vscode from 'vscode';
+import { isConfigFile } from './helpers';
+import { updateDiagnostics } from './diagnostics';
+
+export const registerDocumentListeners = (context: vscode.ExtensionContext, collection: vscode.DiagnosticCollection) => {
+    context.subscriptions.push(
+        vscode.workspace.onDidOpenTextDocument(document => {
+            if (!isConfigFile(document)) {
+                return;
+            }
+            updateDiagnostics(document, collection);
+        })
+    );
+
+    context.subscriptions.push(
+        vscode.workspace.onDidChangeTextDocument(event => {
+            if (!isConfigFile(event.document)) {
+                collection.delete(event.document.uri);
+                return;
+            }
+            updateDiagnostics(event.document, collection);
+        })
+    );
+};
\ No newline at end of file
diff --git a/src/extension.ts b/src/extension.ts
index 035d104..008a26c 100644
--- a/src/extension.ts
+++ b/src/extension.ts
@@ -1,167 +1,19 @@
 import * as vscode from 'vscode';
-import parse from 'json-to-ast';
-import {pluginDocs, pluginSnippets} from './constants';
-import {getASTNode, getRangeFromASTNode, isConfigFile} from './helpers';
-import {pluginLensProvider} from './codelens';
+import { registerCommands } from './commands';
+import { detectDevProxyInstall } from './detect';
+import { handleStartNotification, processNotification } from './notifications';
+import { registerDocumentListeners } from './documents';
+import { registerCodeLens } from './codelens';
 
-export const activate = (context: vscode.ExtensionContext) => {
+export const activate = async (context: vscode.ExtensionContext) => {
   const collection = vscode.languages.createDiagnosticCollection('Dev Proxy');
-
-  context.subscriptions.push(
-    vscode.workspace.onDidOpenTextDocument(document => {
-      if (!isConfigFile(document)) {
-        return;
-      }
-      updateDiagnostics(document, collection);
-    })
-  );
-
-  context.subscriptions.push(
-    vscode.workspace.onDidChangeTextDocument(event => {
-      if (!isConfigFile(event.document)) {
-        collection.delete(event.document.uri);
-        return;
-      }
-      updateDiagnostics(event.document, collection);
-    })
-  );
-
-  context.subscriptions.push(
-    vscode.languages.registerCodeLensProvider(
-      {scheme: 'file', language: 'json'},
-      pluginLensProvider
-    )
-  );
-
-  context.subscriptions.push(
-    vscode.commands.registerCommand(
-      'dev-proxy-toolkit.openPluginDoc',
-      pluginName => {
-        const target = vscode.Uri.parse(pluginDocs[pluginName].url);
-        vscode.env.openExternal(target);
-      }
-    )
-  );
-};
-
-const updateDiagnostics = (
-  document: vscode.TextDocument,
-  collection: vscode.DiagnosticCollection
-): void => {
-  let diagnostics: vscode.Diagnostic[] = [];
-
-  const documentNode = parse(document.getText()) as parse.ObjectNode;
-
-  // check if urlsToWatch is empty
-  const urlsToWatchNode = getASTNode(
-    documentNode.children,
-    'Identifier',
-    'urlsToWatch'
-  );
-  if (
-    urlsToWatchNode &&
-    (urlsToWatchNode.value as parse.ArrayNode).children.length === 0
-  ) {
-    diagnostics.push(
-      new vscode.Diagnostic(
-        getRangeFromASTNode(urlsToWatchNode),
-        'Add at least one url to watch.',
-        vscode.DiagnosticSeverity.Error
-      )
-    );
-  }
-
-  // check validity of plugins
-  const pluginsNode = getASTNode(
-    documentNode.children,
-    'Identifier',
-    'plugins'
-  );
-  if (
-    pluginsNode &&
-    (pluginsNode.value as parse.ArrayNode).children.length !== 0
-  ) {
-    const pluginNodes = (pluginsNode.value as parse.ArrayNode)
-      .children as parse.ObjectNode[];
-
-    // check for plugins
-    if (pluginNodes.length === 0) {
-      diagnostics.push(
-        new vscode.Diagnostic(
-          getRangeFromASTNode(pluginsNode),
-          'Add at least one plugin',
-          vscode.DiagnosticSeverity.Error
-        )
-      );
-    }
-
-    // does the plugin have a config section?
-    pluginNodes.forEach((pluginNode: parse.ObjectNode) => {
-      const pluginNameNode = getASTNode(
-        pluginNode.children,
-        'Identifier',
-        'name'
-      );
-      const pluginName = (pluginNameNode?.value as parse.LiteralNode)
-        .value as string;
-      const enabledNode = getASTNode(
-        pluginNode.children,
-        'Identifier',
-        'enabled'
-      );
-      const isEnabled = (enabledNode?.value as parse.LiteralNode)
-        .value as boolean;
-      const pluginSnippet = pluginSnippets[pluginName];
-      const requiresConfig = pluginSnippet.config
-        ? pluginSnippet.config.required
-        : false;
-
-      if (requiresConfig) {
-        // check to see if the plugin has a config section
-        const configSectionNode = getASTNode(
-          pluginNode.children,
-          'Identifier',
-          'configSection'
-        );
-        if (!configSectionNode) {
-          // there is no config section defined on the plugin instance
-          diagnostics.push(
-            new vscode.Diagnostic(
-              getRangeFromASTNode(pluginNode),
-              `${pluginName} requires a config section.`,
-              isEnabled
-                ? vscode.DiagnosticSeverity.Error
-                : vscode.DiagnosticSeverity.Warning
-            )
-          );
-        } else {
-          // check to see if the config section is in the document
-          const configSectionName = (
-            configSectionNode.value as parse.LiteralNode
-          ).value as string;
-          const configSection = getASTNode(
-            documentNode.children,
-            'Identifier',
-            configSectionName
-          );
-
-          if (!configSection) {
-            diagnostics.push(
-              new vscode.Diagnostic(
-                getRangeFromASTNode(configSectionNode.value),
-                `${configSectionName} config section is missing. Use '${pluginSnippet.config?.name}' snippet to create one.`,
-                isEnabled
-                  ? vscode.DiagnosticSeverity.Error
-                  : vscode.DiagnosticSeverity.Warning
-              )
-            );
-          }
-        }
-      }
-    });
-  }
-
-  collection.set(document.uri, diagnostics);
+  registerDocumentListeners(context, collection);
+  registerCommands(context);
+  registerCodeLens(context);
+  
+  const devProxyInstall = await detectDevProxyInstall();
+  const notification = handleStartNotification(devProxyInstall);
+  processNotification(notification);
 };
 
-export const deactivate = () => {};
+export const deactivate = () => { };
diff --git a/src/notifications.ts b/src/notifications.ts
new file mode 100644
index 0000000..46d7755
--- /dev/null
+++ b/src/notifications.ts
@@ -0,0 +1,23 @@
+import * as vscode from 'vscode';
+import { DevProxyInstall } from './types';
+
+export const handleStartNotification = (devProxyInstall: DevProxyInstall) => {
+    if (!devProxyInstall.isInstalled) {
+        return () => {
+            const message = `Dev Proxy is not installed, or not in PATH.`;
+            return {
+                message,
+                show: async () => {
+                    const result = await vscode.window.showInformationMessage(message, 'Install');
+                    if (result === 'Install') {
+                        await vscode.commands.executeCommand('dev-proxy-toolkit.install', devProxyInstall.platform);
+                    };
+                }
+            };
+        };
+    };
+};
+
+export const processNotification = (notification: (() => { message: string; show: () => Promise<void>; }) | undefined) => {
+    if (notification) { notification().show(); };
+};
diff --git a/src/test/extension.test.ts b/src/test/extension.test.ts
index 3135ba9..bcb4980 100644
--- a/src/test/extension.test.ts
+++ b/src/test/extension.test.ts
@@ -9,41 +9,16 @@ import {
 } from '../helpers';
 import * as path from 'path';
 import parse from 'json-to-ast';
-import {createCodeLensForPluginNodes} from '../codelens';
-
-suite('Extension Test Suite', () => {
-  test('should activate when untitled JSON file is opened', async () => {
-    const extensionId = 'garrytrinder.dev-proxy-toolkit';
-    await vscode.workspace.openTextDocument({
-      language: 'json',
-      content: '',
-    });
-    await sleep(1000);
-
-    const expected = true;
-    const actual = vscode.extensions.getExtension(extensionId)?.isActive;
-    assert.strictEqual(actual, expected);
-  });
-
-  test('should activate when JSON file is opened from disk', async () => {
-    const extensionId = 'garrytrinder.dev-proxy-toolkit';
-    const fileName = 'foo.json';
-    const filePath = path.resolve(__dirname, 'examples', fileName);
-    await vscode.workspace.openTextDocument(filePath);
-    await sleep(1000);
-
-    const expected = true;
-    const actual = vscode.extensions.getExtension(extensionId)?.isActive;
-    assert.strictEqual(actual, expected);
-  });
-});
+import { createCodeLensForPluginNodes } from '../codelens';
+import { DevProxyInstall } from '../types';
+import { handleStartNotification } from '../notifications';
 
 suite('urlsToWatch', () => {
   test('should show error when opening document with no urlsToWatch found', async () => {
     const fileName = 'config-urls-to-watch-required.json';
     const filePath = path.resolve(__dirname, 'examples', fileName);
     const document = await vscode.workspace.openTextDocument(filePath);
-    const diagnostics = vscode.languages.getDiagnostics(document.uri);
+        const diagnostics = vscode.languages.getDiagnostics(document.uri);
 
     const expected = {
       message: 'Add at least one url to watch.',
@@ -258,3 +233,79 @@ suite('plugins', () => {
     assert.strictEqual(actual, expected);
   });
 });
+
+suite('notifications', () => {
+  test('should show install notification when devproxy is not installed on mac', async () => {
+    const devProxyInstall: DevProxyInstall = {
+      filePath: '',
+      version: '',
+      platform: 'darwin',
+      isInstalled: false,
+      isBeta: false,
+    };
+    const notification = handleStartNotification(devProxyInstall);
+
+    const expected = 'Dev Proxy is not installed, or not in PATH.';
+    const actual = notification !== undefined && notification().message;
+    assert.strictEqual(actual, expected);
+  });
+
+  test('should show install notification when devproxy is not installed on windows', async () => {
+    const devProxyInstall: DevProxyInstall = {
+      filePath: '',
+      version: '',
+      platform: 'win32',
+      isInstalled: false,
+      isBeta: false,
+    };
+    const notification = handleStartNotification(devProxyInstall);
+
+    const expected = 'Dev Proxy is not installed, or not in PATH.';
+    const actual = notification !== undefined && notification().message;
+    assert.strictEqual(actual, expected);
+  });
+
+  test('should not show install notification when devproxy is installed on mac', async () => {
+    const devProxyInstall: DevProxyInstall = {
+      filePath: 'somepath/devproxy',
+      version: '0.1.0',
+      platform: 'darwin',
+      isInstalled: true,
+      isBeta: false,
+    };
+    const notification = handleStartNotification(devProxyInstall);
+
+    const expected = true;
+    const actual = notification === undefined;
+  });
+
+  test('should not show install notification when devproxy is installed on windows', async () => {
+    const devProxyInstall: DevProxyInstall = {
+      filePath: 'somepath/devproxy',
+      version: '0.1.0',
+      platform: 'win32',
+      isInstalled: true,
+      isBeta: false,
+    };
+    const notification = handleStartNotification(devProxyInstall);
+
+    const expected = true;
+    const actual = notification === undefined;
+    assert.strictEqual(actual, expected);
+  });
+
+  test('should not show install notification when running in unsupported operating system', async () => {
+    const devProxyInstall: DevProxyInstall = {
+      filePath: 'somepath/devproxy',
+      version: '0.1.0',
+      platform: 'linux',
+      isInstalled: true,
+      isBeta: false,
+    };
+    const notification = handleStartNotification(devProxyInstall);
+
+    const expected = true;
+    const actual = notification === undefined;
+    assert.strictEqual(actual, expected);
+  });
+});
\ No newline at end of file
diff --git a/src/types.ts b/src/types.ts
index 6ba361c..12cb2f0 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -16,3 +16,11 @@ export type PluginSnippets = {
     config?: PluginConfig;
   };
 };
+
+export type DevProxyInstall = {
+  filePath: string;
+  version: string;
+  isInstalled: boolean;
+  isBeta: boolean;
+  platform: NodeJS.Platform;
+};
\ No newline at end of file