Page Visibility API Blocker

Chrome extension that comprehensively blocks the Page Visibility API and related detection vectors to prevent websites from detecting when the page is hidden or minimized.

Installation

1. Open Chrome and navigate to chrome://extensions/
2. Enable "Developer mode" in the top right corner
3. Click "Load unpacked"
4. Select this directory

Usage

1. Click the extension icon in the Chrome toolbar
2. Toggle the "Block API" switch to enable or disable blocking
3. Pages will reload automatically when you change the state

How It Works

When enabled, the extension blocks all known visibility detection vectors:

Page Visibility API

• Overrides Document.prototype.hidden to always return false
• Overrides Document.prototype.visibilityState to always return 'visible'
• Blocks visibilitychange event listeners via addEventListener
• Blocks document.onvisibilitychange handler property assignments

Focus Detection

• Overrides document.hasFocus() to always return true
• Blocks blur and focus event listeners on window
• Blocks window.onblur and window.onfocus handler property assignments

Anti-Detection

• All API overrides are applied at the prototype level (Document.prototype, Window.prototype) to prevent bypass via Object.getOwnPropertyDescriptor
• State communication uses a short, non-descriptive DOM attribute instead of a named <meta> tag
• Blocked listeners are tracked properly so removeEventListener behaves correctly

Files

• manifest.json - Extension configuration (Manifest V3)
• popup.html - Extension popup interface
• popup.js - Popup logic and state management
• background.js - Background service worker
• state_injector.js - Sets blocking state in DOM for the MAIN world script (ISOLATED world)
• blocker.js - Comprehensive Page Visibility API blocking (MAIN world)
• test.html - Test suite to verify all blocking vectors
• Icon.png - Extension icon

Limitations

• Websites may use requestAnimationFrame timing to infer tab backgrounding (extremely difficult to block from an extension)
• Page Lifecycle API events (freeze/resume) are not currently blocked
• Blocking may cause pages to continue resource-intensive operations when hidden
• Pages must be reloaded after changing the enabled/disabled state