User-Agent Changer Autor: Shawon2901

Author: Shawon2901 · Version: 2.0 · Manifest: V2 · Min Firefox: 142.0
A Firefox extension that replaces your browser's User-Agent header at the network level (via webRequest), making web servers see a completely different browser/OS than what you're actually using.
How It Works
The extension intercepts every outgoing HTTP request via webRequest.onBeforeSendHeaders and rewrites the User-Agent header before it leaves the browser. This is a true network-level spoof — it affects server-side detection, not just navigator.userAgent in JavaScript.
Features
50+ Preset User Agents across 9 categories:
🤖 Chrome Android (Galaxy S25, Pixel 9 Pro, generic)
💻 Chrome Desktop (Windows, macOS, Linux)
🍏 Chrome iOS / CriOS (iPhone, iPad)
🌀 Microsoft Edge (desktop + mobile)
🧭 Safari (iPhone, iPad, macOS)
🦊 Firefox (Android, Windows, macOS, Linux)
📱 Samsung Internet
🎭 Opera / Opera GX
🤖 Bots & Crawlers
Two Domain Filtering Modes:
Exclusion mode — spoof everywhere except domains in the "Always Real" list (default)
Inclusion mode — spoof only domains explicitly listed in the "Include Only" list
Always-Real List: Certain domains (e.g. cloudflare.com, 1.1.1.1) always receive the real UA regardless of mode, preventing auth/CAPTCHA breakage on sensitive services.
intent:// URL Handling: Rewrites Android intent:// redirect headers and tab navigations into proper https:// URLs — useful when spoofing mobile UAs causes sites to serve Android deep-link redirects.
Visual Status: Icon desaturates and shows an OFF badge when disabled; tooltip displays the currently active UA label when enabled.
Persistent State: All settings (enabled state, active UA, domain lists, mode) are saved via browser.storage.local.

Use Cases

Bypass server-side browser/OS detection and access restrictions
Test how sites render for different browsers/devices without switching browsers
Reduce device fingerprinting surface
Trigger mobile-optimized responses from desktop Firefox