diff --git a/.eslintignore b/.eslintignore
deleted file mode 100644
index 577d54a5..00000000
--- a/.eslintignore
+++ /dev/null
@@ -1,3 +0,0 @@
-!.*
-*-polyfill.*
-dist
diff --git a/.eslintrc.js b/.eslintrc.js
deleted file mode 100644
index 01103561..00000000
--- a/.eslintrc.js
+++ /dev/null
@@ -1,39 +0,0 @@
-/** @type {import('eslint').Linter.Config} */
-const config = {
-  root: true,
-
-  env: {
-    node: true,
-    es2024: true
-  },
-
-  parserOptions: {
-    ecmaVersion: 'latest',
-    sourceType: 'module',
-    ecmaFeatures: {
-      impliedStrict: true
-    }
-  },
-
-  extends: ['eslint:recommended', 'prettier'],
-
-  rules: {
-    'no-var': 'error',
-    'no-await-in-loop': 'error',
-    'no-implicit-globals': ['error'],
-    'no-unused-vars': ['error', { vars: 'local', argsIgnorePattern: '^_' }],
-    'no-useless-rename': ['error'],
-    'arrow-body-style': ['error', 'as-needed'],
-    'no-lonely-if': 'error',
-    'prefer-object-has-own': 'error',
-    'prefer-exponentiation-operator': 'error',
-    'prefer-regex-literals': ['error', { disallowRedundantWrapping: true }],
-    'array-callback-return': ['error', { checkForEach: true, allowVoid: true }],
-    'no-constant-binary-expression': 'error', // default in 'eslint:recommended' since v9
-    'no-constructor-return': 'error',
-    'no-empty-static-block': 'error', // default in 'eslint:recommended' since v9
-    'no-unmodified-loop-condition': 'error'
-  }
-};
-
-module.exports = config;
diff --git a/.prettierrc.mjs b/.prettierrc.js
similarity index 100%
rename from .prettierrc.mjs
rename to .prettierrc.js
diff --git a/babel.config.mjs b/babel.config.js
similarity index 100%
rename from babel.config.mjs
rename to babel.config.js
diff --git a/eslint.config.js b/eslint.config.js
new file mode 100644
index 00000000..a7653de3
--- /dev/null
+++ b/eslint.config.js
@@ -0,0 +1,90 @@
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import Module from 'node:module';
+
+import eslintJs from '@eslint/js';
+import prettierConfig from 'eslint-config-prettier';
+import globals from 'globals';
+
+const require = Module.createRequire(import.meta.url);
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+/** @type {'module' | 'commonjs'} */
+const defaultSourceType =
+  require(join(__dirname, 'package.json')).type ?? 'commonjs';
+
+/** @type {import('eslint').Linter.FlatConfig[]} */
+export default [
+  eslintJs.configs.recommended,
+  prettierConfig,
+
+  {
+    linterOptions: {
+      reportUnusedDisableDirectives: 'error'
+    },
+
+    languageOptions: {
+      sourceType: defaultSourceType,
+      parserOptions: {
+        ecmaFeatures: {
+          impliedStrict: true
+        }
+      },
+      globals: {
+        ...globals.nodeBuiltin
+      }
+    },
+
+    rules: {
+      'no-var': 'error',
+      'no-await-in-loop': 'error',
+      'no-implicit-globals': ['error'],
+      'no-unused-vars': ['error', { vars: 'local', argsIgnorePattern: '^_' }],
+      'no-useless-rename': ['error'],
+      'arrow-body-style': ['error', 'as-needed'],
+      'no-lonely-if': 'error',
+      'prefer-object-has-own': 'error',
+      'prefer-exponentiation-operator': 'error',
+      'prefer-regex-literals': ['error', { disallowRedundantWrapping: true }],
+      'array-callback-return': [
+        'error',
+        { checkForEach: true, allowVoid: true }
+      ],
+      'no-constant-binary-expression': 'error', // default in 'eslint:recommended' since v9
+      'no-constructor-return': 'error',
+      'no-empty-static-block': 'error', // default in 'eslint:recommended' since v9
+      'no-unmodified-loop-condition': 'error'
+    }
+  },
+
+  {
+    files: ['src/**/*'],
+    languageOptions: {
+      globals: {
+        ...globals.browser
+      }
+    }
+  },
+
+  {
+    // Why doesn't ESLint do this by default is beyond me.
+    files: ['**/*.cjs'],
+    languageOptions: {
+      sourceType: 'commonjs'
+    }
+  },
+
+  {
+    // Why doesn't ESLint do this by default is beyond me.
+    files: ['**/*.mjs'],
+    languageOptions: {
+      sourceType: 'module'
+    }
+  },
+
+  {
+    // `ignores` field must be in the very bottom config.
+    ignores: ['dist/**/*', '**/*-polyfill.*']
+  }
+];
diff --git a/package-lock.json b/package-lock.json
index f2f537c3..799e2808 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -19,6 +19,7 @@
         "@babel/core": "^7.24.3",
         "@babel/plugin-transform-runtime": "^7.24.3",
         "@babel/preset-env": "^7.24.3",
+        "@eslint/js": "^8.57.0",
         "@types/babel__core": "^7.20.5",
         "@webos-tools/cli": "^3.0.2",
         "babel-loader": "^9.1.3",
@@ -28,6 +29,7 @@
         "css-loader": "^6.10.0",
         "eslint": "^8.57.0",
         "eslint-config-prettier": "^9.1.0",
+        "globals": "^15.0.0",
         "husky": "^9.0.11",
         "lint-staged": "^15.2.2",
         "prettier": "^3.2.5",
@@ -901,6 +903,15 @@
         "@babel/core": "^7.0.0-0"
       }
     },
+    "node_modules/@babel/plugin-transform-classes/node_modules/globals": {
+      "version": "11.12.0",
+      "resolved": "https://registry.npmjs.org/globals/-/globals-11.12.0.tgz",
+      "integrity": "sha512-WOBp/EEGUiIsJSp7wcv/y6MO+lV9UoncWqxuFfm8eBwzWNgyfBd6Gz+IeKQ9jCmyhoH99g15M3T+QaVHFjizVA==",
+      "dev": true,
+      "engines": {
+        "node": ">=4"
+      }
+    },
     "node_modules/@babel/plugin-transform-computed-properties": {
       "version": "7.24.1",
       "resolved": "https://registry.npmjs.org/@babel/plugin-transform-computed-properties/-/plugin-transform-computed-properties-7.24.1.tgz",
@@ -1730,6 +1741,15 @@
         "node": ">=6.9.0"
       }
     },
+    "node_modules/@babel/traverse/node_modules/globals": {
+      "version": "11.12.0",
+      "resolved": "https://registry.npmjs.org/globals/-/globals-11.12.0.tgz",
+      "integrity": "sha512-WOBp/EEGUiIsJSp7wcv/y6MO+lV9UoncWqxuFfm8eBwzWNgyfBd6Gz+IeKQ9jCmyhoH99g15M3T+QaVHFjizVA==",
+      "dev": true,
+      "engines": {
+        "node": ">=4"
+      }
+    },
     "node_modules/@babel/types": {
       "version": "7.24.0",
       "resolved": "https://registry.npmjs.org/@babel/types/-/types-7.24.0.tgz",
@@ -8993,12 +9013,15 @@
       "dev": true
     },
     "node_modules/globals": {
-      "version": "11.12.0",
-      "resolved": "https://registry.npmjs.org/globals/-/globals-11.12.0.tgz",
-      "integrity": "sha512-WOBp/EEGUiIsJSp7wcv/y6MO+lV9UoncWqxuFfm8eBwzWNgyfBd6Gz+IeKQ9jCmyhoH99g15M3T+QaVHFjizVA==",
+      "version": "15.0.0",
+      "resolved": "https://registry.npmjs.org/globals/-/globals-15.0.0.tgz",
+      "integrity": "sha512-m/C/yR4mjO6pXDTm9/R/SpYTAIyaUB4EOzcaaMEl7mds7Mshct9GfejiJNQGjHHbdMPey13Kpu4TMbYi9ex1pw==",
       "dev": true,
       "engines": {
-        "node": ">=4"
+        "node": ">=18"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/sindresorhus"
       }
     },
     "node_modules/globby": {
diff --git a/package.json b/package.json
index 4665a045..fede2397 100644
--- a/package.json
+++ b/package.json
@@ -2,17 +2,18 @@
   "name": "youtube-webos",
   "version": "0.3.2",
   "description": "Ad-free YouTube app for webOS",
+  "type": "module",
   "main": "index.js",
   "scripts": {
     "build": "webpack --mode=production",
     "build:dev": "webpack --mode=development",
     "package": "ares-package -n dist",
-    "deploy": "node tools/deploy.mjs",
+    "deploy": "node tools/deploy.js",
     "launch": "ares-launch youtube.leanback.v4",
-    "manifest": "node tools/gen-manifest.js youtube.leanback.v4.manifest.json",
-    "version": "node tools/sync-version.js && git add assets/appinfo.json",
+    "manifest": "node tools/gen-manifest.cjs youtube.leanback.v4.manifest.json",
+    "version": "node tools/sync-version.cjs && git add assets/appinfo.json",
     "prepare": "husky install",
-    "lint": "eslint . --report-unused-disable-directives --max-warnings 0",
+    "lint": "eslint .",
     "prettier-check": "prettier --ignore-path .prettierignore --check ."
   },
   "repository": "github:webosbrew/youtube-webos",
@@ -30,6 +31,7 @@
     "@babel/core": "^7.24.3",
     "@babel/plugin-transform-runtime": "^7.24.3",
     "@babel/preset-env": "^7.24.3",
+    "@eslint/js": "^8.57.0",
     "@types/babel__core": "^7.20.5",
     "@webos-tools/cli": "^3.0.2",
     "babel-loader": "^9.1.3",
@@ -39,6 +41,7 @@
     "css-loader": "^6.10.0",
     "eslint": "^8.57.0",
     "eslint-config-prettier": "^9.1.0",
+    "globals": "^15.0.0",
     "husky": "^9.0.11",
     "lint-staged": "^15.2.2",
     "prettier": "^3.2.5",
diff --git a/src/.eslintrc.js b/src/.eslintrc.js
deleted file mode 100644
index dfc11c26..00000000
--- a/src/.eslintrc.js
+++ /dev/null
@@ -1,11 +0,0 @@
-/* eslint-env node */
-
-/** @type {import('eslint').Linter.Config} */
-const config = {
-  env: {
-    browser: true,
-    node: false
-  }
-};
-
-module.exports = config;
diff --git a/tools/deploy.mjs b/tools/deploy.js
similarity index 100%
rename from tools/deploy.mjs
rename to tools/deploy.js
diff --git a/tools/gen-manifest.js b/tools/gen-manifest.cjs
similarity index 100%
rename from tools/gen-manifest.js
rename to tools/gen-manifest.cjs
diff --git a/tools/sync-version.js b/tools/sync-version.cjs
similarity index 100%
rename from tools/sync-version.js
rename to tools/sync-version.cjs
diff --git a/tsconfig.tooling.json b/tsconfig.tooling.json
index b085334c..ffb86d4d 100644
--- a/tsconfig.tooling.json
+++ b/tsconfig.tooling.json
@@ -3,5 +3,5 @@
   "compilerOptions": {
     "checkJs": true
   },
-  "include": ["./*", "./.*", "./**/.eslintrc.js"]
+  "include": ["./*", "./.*"]
 }
diff --git a/webpack.config.mjs b/webpack.config.js
similarity index 92%
rename from webpack.config.mjs
rename to webpack.config.js
index 9dc5f319..45f2b76a 100644
--- a/webpack.config.mjs
+++ b/webpack.config.js
@@ -25,6 +25,7 @@ const makeConfig = () => [
       rules: [
         {
           test: /\.(?:m|c)?js$/i,
+
           loader: 'babel-loader',
           exclude: [
             // Some module should not be transpiled by Babel
@@ -35,6 +36,10 @@ const makeConfig = () => [
           ],
           options: {
             cacheDirectory: true
+          },
+          resolve: {
+            // File extension DON'T MATTER in a bundler.
+            fullySpecified: false
           }
         },
         {