diff --git a/.eslintrc.js b/.eslintrc.js
index a1de9853eef..a119974e1fe 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -166,6 +166,8 @@ module.exports = {
             default: 'array-simple',
           },
         ],
+        // By default this is a warning but we want it to error.
+        '@typescript-eslint/explicit-module-boundary-types': 2,
       },
     },
     {
diff --git a/package.json b/package.json
index f8c2e63c7e6..6b20c2a4541 100644
--- a/package.json
+++ b/package.json
@@ -72,7 +72,7 @@
     "@commitlint/cli": "^11.0.0",
     "@commitlint/config-conventional": "^11.0.0",
     "@microsoft/api-documenter": "^7.12.7",
-    "@microsoft/api-extractor": "^7.13.1",
+    "@microsoft/api-extractor": "7.15.1",
     "@types/debug": "0.0.31",
     "@types/mime": "^2.0.0",
     "@types/mocha": "^7.0.2",
@@ -82,8 +82,8 @@
     "@types/sinon": "^9.0.4",
     "@types/tar-fs": "^1.16.2",
     "@types/ws": "^7.2.4",
-    "@typescript-eslint/eslint-plugin": "^4.4.0",
-    "@typescript-eslint/parser": "^4.4.0",
+    "@typescript-eslint/eslint-plugin": "4.23.0",
+    "@typescript-eslint/parser": "4.23.0",
     "@web/test-runner": "^0.12.15",
     "commonmark": "^0.28.1",
     "cross-env": "^7.0.2",
@@ -109,7 +109,7 @@
     "standard-version": "^9.0.0",
     "text-diff": "^1.0.1",
     "ts-node": "^9.0.0",
-    "typescript": "^4.1.5"
+    "typescript": "4.2.4"
   },
   "husky": {
     "hooks": {
diff --git a/src/common/EventEmitter.ts b/src/common/EventEmitter.ts
index e75377130f7..88d97762df1 100644
--- a/src/common/EventEmitter.ts
+++ b/src/common/EventEmitter.ts
@@ -21,7 +21,7 @@ export interface CommonEventEmitter {
    */
   addListener(event: EventType, handler: Handler): CommonEventEmitter;
   removeListener(event: EventType, handler: Handler): CommonEventEmitter;
-  emit(event: EventType, eventData?: any): boolean;
+  emit(event: EventType, eventData?: unknown): boolean;
   once(event: EventType, handler: Handler): CommonEventEmitter;
   listenerCount(event: string): number;
 
@@ -98,7 +98,7 @@ export class EventEmitter implements CommonEventEmitter {
    * @param eventData - any data you'd like to emit with the event
    * @returns `true` if there are any listeners, `false` if there are not.
    */
-  emit(event: EventType, eventData?: any): boolean {
+  emit(event: EventType, eventData?: unknown): boolean {
     this.emitter.emit(event, eventData);
     return this.eventListenersCount(event) > 0;
   }
diff --git a/src/common/FileChooser.ts b/src/common/FileChooser.ts
index eb3f4d91c81..d1cbea73a38 100644
--- a/src/common/FileChooser.ts
+++ b/src/common/FileChooser.ts
@@ -76,7 +76,7 @@ export class FileChooser {
   /**
    * Closes the file chooser without selecting any files.
    */
-  cancel() {
+  cancel(): void {
     assert(
       !this._handled,
       'Cannot cancel FileChooser which is already handled!'
diff --git a/src/node/install.ts b/src/node/install.ts
index 373cfbd558d..d7e751f44ef 100644
--- a/src/node/install.ts
+++ b/src/node/install.ts
@@ -26,7 +26,7 @@ const supportedProducts = {
   firefox: 'Firefox Nightly',
 } as const;
 
-export async function downloadBrowser() {
+export async function downloadBrowser(): Promise<void> {
   const downloadHost =
     process.env.PUPPETEER_DOWNLOAD_HOST ||
     process.env.npm_config_puppeteer_download_host ||
@@ -178,7 +178,7 @@ export async function downloadBrowser() {
   }
 }
 
-export function logPolitely(toBeLogged) {
+export function logPolitely(toBeLogged: unknown): void {
   const logLevel = process.env.npm_config_loglevel;
   const logLevelDisplay = ['silent', 'error', 'warn'].indexOf(logLevel) > -1;
 
diff --git a/test/cookies.spec.ts b/test/cookies.spec.ts
index 38f6852527b..ad7339b0d39 100644
--- a/test/cookies.spec.ts
+++ b/test/cookies.spec.ts
@@ -231,13 +231,12 @@ describe('Cookie specs', () => {
           value: 'bar',
         }
       );
-      expectCookieEquals(
-        await page.evaluate(() => {
-          const cookies = document.cookie.split(';');
-          return cookies.map((cookie) => cookie.trim()).sort();
-        }),
-        ['foo=bar', 'password=123456']
-      );
+      const cookieStrings = await page.evaluate(() => {
+        const cookies = document.cookie.split(';');
+        return cookies.map((cookie) => cookie.trim()).sort();
+      });
+
+      expect(cookieStrings).toEqual(['foo=bar', 'password=123456']);
     });
     it('should have |expires| set to |-1| for session cookies', async () => {
       const { page, server } = getTestState();
diff --git a/test/mocha-utils.ts b/test/mocha-utils.ts
index 6d713f1c138..238addfef23 100644
--- a/test/mocha-utils.ts
+++ b/test/mocha-utils.ts
@@ -31,6 +31,7 @@ import rimraf from 'rimraf';
 import expect from 'expect';
 
 import { trackCoverage } from './coverage-utils.js';
+import Protocol from 'devtools-protocol';
 
 const setupServer = async () => {
   const assetsPath = path.join(__dirname, 'assets');
@@ -177,7 +178,10 @@ export const itFailsWindowsUntilDate = (
   return it(description, body);
 };
 
-export const itFailsWindows = (description: string, body: Mocha.Func) => {
+export const itFailsWindows = (
+  description: string,
+  body: Mocha.Func
+): Mocha.Test => {
   if (os.platform() === 'win32') {
     return xit(description, body);
   }
@@ -217,7 +221,7 @@ console.log(
   }`
 );
 
-export const setupTestBrowserHooks = () => {
+export const setupTestBrowserHooks = (): void => {
   before(async () => {
     const browser = await puppeteer.launch(defaultBrowserOptions);
     state.browser = browser;
@@ -229,7 +233,7 @@ export const setupTestBrowserHooks = () => {
   });
 };
 
-export const setupTestPageAndContextHooks = () => {
+export const setupTestPageAndContextHooks = (): void => {
   beforeEach(async () => {
     state.context = await state.browser.createIncognitoBrowserContext();
     state.page = await state.context.newPage();
@@ -244,7 +248,7 @@ export const setupTestPageAndContextHooks = () => {
 
 export const mochaHooks = {
   beforeAll: [
-    async () => {
+    async (): Promise<void> => {
       const { server, httpsServer } = await setupServer();
 
       state.puppeteer = puppeteer;
@@ -259,13 +263,13 @@ export const mochaHooks = {
     coverageHooks.beforeAll,
   ],
 
-  beforeEach: async () => {
+  beforeEach: async (): Promise<void> => {
     state.server.reset();
     state.httpsServer.reset();
   },
 
   afterAll: [
-    async () => {
+    async (): Promise<void> => {
       await state.server.stop();
       state.server = null;
       await state.httpsServer.stop();
@@ -274,12 +278,15 @@ export const mochaHooks = {
     coverageHooks.afterAll,
   ],
 
-  afterEach: () => {
+  afterEach: (): void => {
     sinon.restore();
   },
 };
 
-export const expectCookieEquals = (cookies, expectedCookies) => {
+export const expectCookieEquals = (
+  cookies: Protocol.Network.Cookie[],
+  expectedCookies: Array<Partial<Protocol.Network.Cookie>>
+): void => {
   const { isChrome } = getTestState();
   if (!isChrome) {
     // Only keep standard properties when testing on a browser other than Chrome.
diff --git a/utils/doclint/check_public_api/index.js b/utils/doclint/check_public_api/index.js
index e524e52b6a7..989b78bcee9 100644
--- a/utils/doclint/check_public_api/index.js
+++ b/utils/doclint/check_public_api/index.js
@@ -685,7 +685,8 @@ function compareDocumentations(actual, expected) {
         'Method Page.emulateVisionDeficiency() type',
         {
           actualName: 'string',
-          expectedName: 'Object',
+          expectedName:
+            '"none"|"achromatopsia"|"blurredVision"|"deuteranopia"|"protanopia"|"tritanopia"',
         },
       ],
       [
@@ -849,14 +850,6 @@ function compareDocumentations(actual, expected) {
           expectedName: '...DeleteCookiesRequest',
         },
       ],
-      [
-        'Method Page.emulateVisionDeficiency() type',
-        {
-          actualName: 'string',
-          expectedName:
-            '"none"|"achromatopsia"|"blurredVision"|"deuteranopia"|"protanopia"|"tritanopia"',
-        },
-      ],
       [
         'Method BrowserContext.overridePermissions() permissions',
         {
@@ -885,6 +878,13 @@ function compareDocumentations(actual, expected) {
           expectedName: 'Object',
         },
       ],
+      [
+        'Method EventEmitter.emit() eventData',
+        {
+          actualName: 'Object',
+          expectedName: 'unknown',
+        },
+      ],
     ]);
 
     const expectedForSource = expectedNamingMismatches.get(source);