diff --git a/packages/fake-browser/src/apis/action.test.ts b/packages/fake-browser/src/apis/action.test.ts
new file mode 100644
index 0000000..d991531
--- /dev/null
+++ b/packages/fake-browser/src/apis/action.test.ts
@@ -0,0 +1,92 @@
+import { beforeEach, describe, expect, it } from 'vitest';
+
+// Import your fake browser implementation
+import { fakeBrowser } from '..';
+
+describe('Fake Action API', () => {
+  beforeEach(() => {
+    fakeBrowser.reset();
+  });
+
+  describe('setTitle / getTitle', () => {
+    it('should set and get global title', async () => {
+      const title = 'Test Title';
+      await fakeBrowser.action.setTitle({ title });
+      const result = await fakeBrowser.action.getTitle({});
+      expect(result).toBe(title);
+    });
+
+    it('should set and get tab-specific title', async () => {
+      const tabId = 123;
+      const title = 'Tab Title';
+      await fakeBrowser.action.setTitle({ tabId, title });
+      const result = await fakeBrowser.action.getTitle({ tabId });
+      expect(result).toBe(title);
+    });
+  });
+
+  describe('setBadgeText / getBadgeText', () => {
+    it('should set and get global badge text', async () => {
+      const text = '10';
+      await fakeBrowser.action.setBadgeText({ text });
+      const result = await fakeBrowser.action.getBadgeText({});
+      expect(result).toBe(text);
+    });
+
+    it('should set and get tab-specific badge text', async () => {
+      const tabId = 123;
+      const text = '99+';
+      await fakeBrowser.action.setBadgeText({ tabId, text });
+      const result = await fakeBrowser.action.getBadgeText({ tabId });
+      expect(result).toBe(text);
+    });
+
+    it('should return empty string if no badge text is set', async () => {
+      const result = await fakeBrowser.action.getBadgeText({});
+      expect(result).toBe('');
+    });
+  });
+
+  describe('setBadgeBackgroundColor / getBadgeBackgroundColor', () => {
+    it('should set and get global badge background color', async () => {
+      const color = '#FF0000'; // red
+      await fakeBrowser.action.setBadgeBackgroundColor({ color });
+      const result = await fakeBrowser.action.getBadgeBackgroundColor({});
+      expect(result).toEqual([255, 0, 0, 255]);
+    });
+
+    it('should set and get tab-specific badge background color', async () => {
+      const tabId = 123;
+      const color = '#00FF00'; // green
+      await fakeBrowser.action.setBadgeBackgroundColor({ tabId, color });
+      const result = await fakeBrowser.action.getBadgeBackgroundColor({ tabId });
+      expect(result).toEqual([0, 255, 0, 255]);
+    });
+
+    it('should fallback to default black if color not set', async () => {
+      const result = await fakeBrowser.action.getBadgeBackgroundColor({});
+      expect(result).toEqual([95, 93, 91, 255]);
+    });
+  });
+
+  describe('setBadgeTextColor / getBadgeTextColor', () => {
+    it('should set and get global badge text color', async () => {
+      const color = '#0000FF';
+      fakeBrowser.action.setBadgeTextColor({ color });
+      //@ts-ignore
+      fakeBrowser.action.getBadgeTextColor({}, result => {
+        expect(result).toEqual(color);
+      });
+    });
+
+    it('should set and get tab-specific badge text color', async () => {
+      const tabId = 123;
+      const color = '#00FFFF';
+      fakeBrowser.action.setBadgeTextColor({ tabId, color });
+      //@ts-ignore
+      fakeBrowser.action.getBadgeTextColor({ tabId }, result => {
+        expect(result).toBe(color);
+      });
+    });
+  });
+});
diff --git a/packages/fake-browser/src/apis/action.ts b/packages/fake-browser/src/apis/action.ts
new file mode 100644
index 0000000..cd250be
--- /dev/null
+++ b/packages/fake-browser/src/apis/action.ts
@@ -0,0 +1,182 @@
+import { Action, Tabs } from 'webextension-polyfill';
+import { BrowserOverrides } from '../types';
+import { defineEventWithTrigger } from '../utils/defineEventWithTrigger';
+
+const onClicked =
+  defineEventWithTrigger<(tab: Tabs.Tab, info: Action.OnClickData | undefined) => void>();
+
+let DEFAULT_BADGE_BACKGROUND_COLOR = '#5F5D5B';
+let DEFAULT_BADGE_TEXT_COLOR = '#FFFFFF';
+type ColorArray = [number, number, number, number];
+const badgeTextColorState: ScopedState<string> = {
+  global: DEFAULT_BADGE_TEXT_COLOR,
+  tabs: new Map(),
+  windows: new Map(),
+};
+
+interface ScopedState<T> {
+  global?: T;
+  tabs: Map<number, T>;
+  windows: Map<number, T>;
+}
+
+const badgeTextState: ScopedState<string> = {
+  global: '',
+  tabs: new Map(),
+  windows: new Map(),
+};
+
+const badgeBackgroundColorState: ScopedState<ColorArray> = {
+  global: hexToRgbaArray(DEFAULT_BADGE_BACKGROUND_COLOR),
+  tabs: new Map(),
+  windows: new Map(),
+};
+
+const titleState: ScopedState<string> = {
+  global: '',
+  tabs: new Map(),
+  windows: new Map(),
+};
+
+function hexToRgbaArray(hex: string): ColorArray {
+  hex = hex.replace('#', '');
+  let hasAlpha = hex.length === 8;
+  let bigint = parseInt(hex, 16);
+  let r = (bigint >> (hasAlpha ? 24 : 16)) & 255;
+  let g = (bigint >> (hasAlpha ? 16 : 8)) & 255;
+  let b = (bigint >> (hasAlpha ? 8 : 0)) & 255;
+  let a = hasAlpha ? bigint & 255 : 255;
+  return [r, g, b, a];
+}
+
+function getScopedValue<T>(state: ScopedState<T>, details?: Action.Details): T | undefined {
+  if (!details) return state.global;
+  const { tabId, windowId } = details;
+  if (tabId !== undefined) return state.tabs.get(tabId);
+  if (windowId !== undefined) return state.windows.get(windowId);
+  return state.global;
+}
+
+export const action: BrowserOverrides['action'] = {
+  resetState() {
+    onClicked.removeAllListeners();
+    badgeTextState.global = '';
+    badgeTextState.tabs.clear();
+    badgeTextState.windows.clear();
+
+    badgeBackgroundColorState.global = hexToRgbaArray(DEFAULT_BADGE_BACKGROUND_COLOR);
+    badgeBackgroundColorState.tabs.clear();
+    badgeBackgroundColorState.windows.clear();
+
+    titleState.global = '';
+    titleState.tabs.clear();
+    titleState.windows.clear();
+  },
+
+  setTitle(details: Action.SetTitleDetailsType) {
+    const { title, tabId, windowId } = details;
+    if (tabId !== undefined) {
+      if (title === null || title === undefined) {
+        titleState.tabs.delete(tabId);
+      } else {
+        titleState.tabs.set(tabId, title);
+      }
+    } else if (windowId !== undefined) {
+      if (title === null || title === undefined) {
+        titleState.windows.delete(windowId);
+      } else {
+        titleState.windows.set(windowId, title);
+      }
+    } else {
+      titleState.global = title ?? '';
+    }
+    return Promise.resolve();
+  },
+
+  getTitle(details: Action.Details): Promise<string> {
+    const value = getScopedValue(titleState, details);
+    return Promise.resolve(value ?? '');
+  },
+
+  setBadgeText(details: Action.SetBadgeTextDetailsType) {
+    const { text, tabId, windowId } = details;
+    if (tabId !== undefined) {
+      if (text === null || text === undefined) {
+        badgeTextState.tabs.delete(tabId);
+      } else {
+        badgeTextState.tabs.set(tabId, text);
+      }
+    } else if (windowId !== undefined) {
+      if (text === null || text === undefined) {
+        badgeTextState.windows.delete(windowId);
+      } else {
+        badgeTextState.windows.set(windowId, text);
+      }
+    } else {
+      badgeTextState.global = text ?? '';
+    }
+    return Promise.resolve();
+  },
+
+  getBadgeText(details: Action.Details): Promise<string> {
+    const value = getScopedValue(badgeTextState, details);
+    return Promise.resolve(value ?? '');
+  },
+
+  setBadgeBackgroundColor(details: Action.SetBadgeBackgroundColorDetailsType) {
+    const { color, tabId, windowId } = details;
+    let rgbaColor: ColorArray;
+
+    if (typeof color === 'string') {
+      rgbaColor = hexToRgbaArray(color);
+    } else if (Array.isArray(color)) {
+      rgbaColor = [...color] as ColorArray;
+    } else {
+      rgbaColor = hexToRgbaArray(DEFAULT_BADGE_BACKGROUND_COLOR);
+    }
+
+    if (tabId !== undefined) {
+      badgeBackgroundColorState.tabs.set(tabId, rgbaColor);
+    } else if (windowId !== undefined) {
+      badgeBackgroundColorState.windows.set(windowId, rgbaColor);
+    } else {
+      badgeBackgroundColorState.global = rgbaColor;
+    }
+
+    return Promise.resolve();
+  },
+
+  getBadgeBackgroundColor(details: Action.Details): Promise<ColorArray> {
+    const value = getScopedValue(badgeBackgroundColorState, details);
+    return Promise.resolve(value ?? hexToRgbaArray(DEFAULT_BADGE_BACKGROUND_COLOR));
+  },
+
+  setBadgeTextColor(details: Action.SetBadgeTextColorDetailsType) {
+    const { color, tabId, windowId } = details;
+
+    let normalizedColor = typeof color === 'string' ? color : DEFAULT_BADGE_TEXT_COLOR;
+
+    if (tabId !== undefined) {
+      if (color === null || color === undefined) {
+        badgeTextColorState.tabs.delete(tabId);
+      } else {
+        badgeTextColorState.tabs.set(tabId, normalizedColor);
+      }
+    } else if (windowId !== undefined) {
+      if (color === null || color === undefined) {
+        badgeTextColorState.windows.delete(windowId);
+      } else {
+        badgeTextColorState.windows.set(windowId, normalizedColor);
+      }
+    } else {
+      badgeTextColorState.global = normalizedColor;
+    }
+  },
+
+  getBadgeTextColor(details: Action.Details, callback?: (value: string) => void): void {
+    const value = getScopedValue(badgeTextColorState, details);
+    callback?.(value ?? DEFAULT_BADGE_TEXT_COLOR);
+  },
+
+  onClicked,
+};
diff --git a/packages/fake-browser/src/index.ts b/packages/fake-browser/src/index.ts
index ae0b989..85f4e75 100644
--- a/packages/fake-browser/src/index.ts
+++ b/packages/fake-browser/src/index.ts
@@ -5,6 +5,7 @@ import { storage } from './apis/storage';
 import { tabs } from './apis/tabs';
 import { webNavigation } from './apis/webNavigation';
 import { windows } from './apis/windows';
+import { action } from './apis/action';
 import { BrowserOverrides, FakeBrowser } from './types';
 import { GeneratedBrowser } from './base.gen';
 import merge from 'lodash.merge';
@@ -26,6 +27,7 @@ const overrides: BrowserOverrides = {
   tabs,
   webNavigation,
   windows,
+  action,
 };
 
 /**
diff --git a/packages/fake-browser/src/types.ts b/packages/fake-browser/src/types.ts
index d0e820a..c345e55 100644
--- a/packages/fake-browser/src/types.ts
+++ b/packages/fake-browser/src/types.ts
@@ -1,4 +1,5 @@
 import type {
+  Action,
   Alarms,
   Browser,
   Notifications,
@@ -107,6 +108,20 @@ export interface BrowserOverrides {
     onRemoved: EventForTesting<[windowId: number]>;
     onFocusChanged: EventForTesting<[windowId: number]>;
   };
+  action: Pick<
+    Action.Static,
+    | 'setTitle'
+    | 'getTitle'
+    | 'getBadgeText'
+    | 'setBadgeText'
+    | 'setBadgeTextColor'
+    | 'getBadgeTextColor'
+    | 'getBadgeBackgroundColor'
+    | 'setBadgeBackgroundColor'
+  > & {
+    resetState(): void;
+    onClicked: EventForTesting<[tab: Tabs.Tab, info: Action.OnClickData | undefined]>;
+  };
 }
 
 /**