diff --git a/packages/docusaurus-plugin-client-redirects/src/writeRedirectFiles.ts b/packages/docusaurus-plugin-client-redirects/src/writeRedirectFiles.ts
index 04cbafcc5001..9c3f3cbd6d29 100644
--- a/packages/docusaurus-plugin-client-redirects/src/writeRedirectFiles.ts
+++ b/packages/docusaurus-plugin-client-redirects/src/writeRedirectFiles.ts
@@ -20,7 +20,7 @@ export type RedirectFileMetadata = {
   fileContent: string;
 };
 
-export function createToUrl(baseUrl: string, to: string) {
+export function createToUrl(baseUrl: string, to: string): string {
   return normalizeUrl([baseUrl, to]);
 }
 
diff --git a/packages/docusaurus-plugin-content-docs/src/theme/hooks/useDocs.ts b/packages/docusaurus-plugin-content-docs/src/theme/hooks/useDocs.ts
index 6e14f3106c84..fbf0d2115558 100644
--- a/packages/docusaurus-plugin-content-docs/src/theme/hooks/useDocs.ts
+++ b/packages/docusaurus-plugin-content-docs/src/theme/hooks/useDocs.ts
@@ -18,8 +18,10 @@ import {
   getActiveVersion,
   getActiveDocContext,
   getDocVersionSuggestions,
-  GetActivePluginOptions,
   ActivePlugin,
+  ActiveDocContext,
+  DocVersionSuggestions,
+  GetActivePluginOptions,
 } from '../../client/docsClientUtils';
 
 export const useAllDocsData = (): Record<string, GlobalPluginData> =>
@@ -28,7 +30,9 @@ export const useAllDocsData = (): Record<string, GlobalPluginData> =>
 export const useDocsData = (pluginId: string | undefined) =>
   usePluginData('docusaurus-plugin-content-docs', pluginId) as GlobalPluginData;
 
-export const useActivePlugin = (options: GetActivePluginOptions = {}) => {
+export const useActivePlugin = (
+  options: GetActivePluginOptions = {},
+): ActivePlugin | undefined => {
   const data = useAllDocsData();
   const {pathname} = useLocation();
   return getActivePlugin(data, pathname, options);
@@ -57,27 +61,35 @@ export const useVersions = (pluginId: string | undefined): GlobalVersion[] => {
   return data.versions;
 };
 
-export const useLatestVersion = (pluginId: string | undefined) => {
+export const useLatestVersion = (
+  pluginId: string | undefined,
+): GlobalVersion => {
   const data = useDocsData(pluginId);
   return getLatestVersion(data);
 };
 
 // Note: return undefined on doc-unrelated pages,
 // because there's no version currently considered as active
-export const useActiveVersion = (pluginId: string | undefined) => {
+export const useActiveVersion = (
+  pluginId: string | undefined,
+): GlobalVersion | undefined => {
   const data = useDocsData(pluginId);
   const {pathname} = useLocation();
   return getActiveVersion(data, pathname);
 };
 
-export const useActiveDocContext = (pluginId: string | undefined) => {
+export const useActiveDocContext = (
+  pluginId: string | undefined,
+): ActiveDocContext => {
   const data = useDocsData(pluginId);
   const {pathname} = useLocation();
   return getActiveDocContext(data, pathname);
 };
 
 // Useful to say "hey, you are not on the latest docs version, please switch"
-export const useDocVersionSuggestions = (pluginId: string | undefined) => {
+export const useDocVersionSuggestions = (
+  pluginId: string | undefined,
+): DocVersionSuggestions => {
   const data = useDocsData(pluginId);
   const {pathname} = useLocation();
   return getDocVersionSuggestions(data, pathname);
diff --git a/packages/docusaurus-theme-common/src/utils/generalUtils.ts b/packages/docusaurus-theme-common/src/utils/generalUtils.ts
index 5bdfe981586b..14ab2b24b9af 100644
--- a/packages/docusaurus-theme-common/src/utils/generalUtils.ts
+++ b/packages/docusaurus-theme-common/src/utils/generalUtils.ts
@@ -6,7 +6,7 @@
  */
 import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
 
-export const useTitleFormatter = (title?: string | undefined) => {
+export const useTitleFormatter = (title?: string | undefined): string => {
   const {siteConfig = {}} = useDocusaurusContext();
   const {title: siteTitle, titleDelimiter = '|'} = siteConfig;
   return title && title.trim().length
diff --git a/packages/docusaurus-utils-validation/src/__tests__/validationSchemas.test.ts b/packages/docusaurus-utils-validation/src/__tests__/validationSchemas.test.ts
index 39a4ee55be67..0bff8248eb66 100644
--- a/packages/docusaurus-utils-validation/src/__tests__/validationSchemas.test.ts
+++ b/packages/docusaurus-utils-validation/src/__tests__/validationSchemas.test.ts
@@ -28,7 +28,6 @@ function createTestHelpers({
 
   function testFail(value: unknown) {
     expect(() => Joi.attempt(value, schema)).toThrowErrorMatchingSnapshot(
-      // @ts-expect-error: seems ok at runtime, but bad typedef
       `for value=${JSON.stringify(value)}`,
     );
   }
diff --git a/packages/docusaurus-utils-validation/src/validationUtils.ts b/packages/docusaurus-utils-validation/src/validationUtils.ts
index 5a270dc4f243..9a919a4e6a97 100644
--- a/packages/docusaurus-utils-validation/src/validationUtils.ts
+++ b/packages/docusaurus-utils-validation/src/validationUtils.ts
@@ -38,7 +38,7 @@ export const logValidationBugReportHint = (): void => {
 export function normalizePluginOptions<T extends {id?: string}>(
   schema: Joi.ObjectSchema<T>,
   options: unknown,
-) {
+): T {
   // All plugins can be provided an "id" option (multi-instance support)
   // we add schema validation automatically
   const finalSchema = schema.append({
@@ -51,7 +51,7 @@ export function normalizePluginOptions<T extends {id?: string}>(
     logValidationBugReportHint();
     if (isValidationDisabledEscapeHatch) {
       console.error(error);
-      return options;
+      return options as T;
     } else {
       throw error;
     }
@@ -62,7 +62,7 @@ export function normalizePluginOptions<T extends {id?: string}>(
 export function normalizeThemeConfig<T>(
   schema: Joi.ObjectSchema<T>,
   themeConfig: unknown,
-) {
+): T {
   // A theme should only validate his "slice" of the full themeConfig,
   // not the whole object, so we allow unknown attributes
   // otherwise one theme would fail validating the data of another theme
@@ -76,7 +76,7 @@ export function normalizeThemeConfig<T>(
     logValidationBugReportHint();
     if (isValidationDisabledEscapeHatch) {
       console.error(error);
-      return themeConfig;
+      return themeConfig as T;
     } else {
       throw error;
     }
diff --git a/packages/docusaurus/src/client/flat.ts b/packages/docusaurus/src/client/flat.ts
index 042e5f2e3a71..4525eb19260b 100644
--- a/packages/docusaurus/src/client/flat.ts
+++ b/packages/docusaurus/src/client/flat.ts
@@ -6,7 +6,7 @@
  */
 
 // Too dynamic
-// eslint-disable-next-line @typescript-eslint/no-explicit-any
+/* eslint-disable @typescript-eslint/no-explicit-any */
 function flat(target: unknown): Record<string, any> {
   const delimiter = '.';
   const output: Record<string, any> = {};
diff --git a/packages/docusaurus/src/commands/writeHeadingIds.ts b/packages/docusaurus/src/commands/writeHeadingIds.ts
index 4661ccb4b34a..40198f293e5a 100644
--- a/packages/docusaurus/src/commands/writeHeadingIds.ts
+++ b/packages/docusaurus/src/commands/writeHeadingIds.ts
@@ -15,11 +15,11 @@ import initPlugins from '../server/plugins/init';
 import {flatten} from 'lodash';
 import {parseMarkdownHeadingId} from '@docusaurus/utils';
 
-export function unwrapMarkdownLinks(line) {
+export function unwrapMarkdownLinks(line: string): string {
   return line.replace(/\[([^\]]+)\]\([^)]+\)/g, (match, p1) => p1);
 }
 
-function addHeadingId(line, slugger) {
+function addHeadingId(line: string, slugger: GithubSlugger): string {
   let headingLevel = 0;
   while (line.charAt(headingLevel) === '#') {
     headingLevel += 1;
@@ -35,7 +35,7 @@ function addHeadingId(line, slugger) {
 export function transformMarkdownHeadingLine(
   line: string,
   slugger: GithubSlugger,
-) {
+): string {
   if (!line.startsWith('#')) {
     throw new Error(`Line is not a markdown heading: ${line}`);
   }
diff --git a/packages/docusaurus/src/server/translations/translationsExtractor.ts b/packages/docusaurus/src/server/translations/translationsExtractor.ts
index c08cb4550267..001cea522d5f 100644
--- a/packages/docusaurus/src/server/translations/translationsExtractor.ts
+++ b/packages/docusaurus/src/server/translations/translationsExtractor.ts
@@ -32,7 +32,7 @@ function isTranslatableSourceCodePath(filePath: string): boolean {
   return TranslatableSourceCodeExtension.has(nodePath.extname(filePath));
 }
 
-function getSiteSourceCodeFilePaths(siteDir): string[] {
+function getSiteSourceCodeFilePaths(siteDir: string): string[] {
   return [nodePath.join(siteDir, SRC_DIR_NAME)];
 }
 
@@ -180,7 +180,7 @@ function extractSourceCodeAstTranslations(
     return `File=${sourceCodeFilePath} at line=${node.loc?.start.line}`;
   }
   function generateCode(node: Node) {
-    return generate(node as any).code;
+    return generate(node).code;
   }
 
   const translations: Record<string, TranslationMessage> = {};
diff --git a/packages/docusaurus/src/webpack/plugins/WaitPlugin.ts b/packages/docusaurus/src/webpack/plugins/WaitPlugin.ts
index e626504abaa1..4fbff0c26f4f 100644
--- a/packages/docusaurus/src/webpack/plugins/WaitPlugin.ts
+++ b/packages/docusaurus/src/webpack/plugins/WaitPlugin.ts
@@ -21,7 +21,7 @@ export default class WaitPlugin {
     this.filepath = options.filepath;
   }
 
-  apply(compiler: Compiler) {
+  apply(compiler: Compiler): void {
     // Before finishing the compilation step
     compiler.hooks.make.tapAsync('WaitPlugin', (compilation, callback) => {
       // To prevent 'waitFile' error on waiting non-existing directory
diff --git a/packages/docusaurus/tsconfig.json b/packages/docusaurus/tsconfig.json
index 5276f6f4d114..cec1ef7143af 100644
--- a/packages/docusaurus/tsconfig.json
+++ b/packages/docusaurus/tsconfig.json
@@ -7,7 +7,7 @@
     "rootDir": "src",
     "outDir": "lib",
     "noImplicitAny": false,
-    "jsx": "react",
+    "jsx": "react"
   },
   "exclude": ["node_modules", "**/__tests__/**/*", "**/lib/**/*", "src/client"]
 }