User-Agent Changer 作者： Shawon2901

🚀 OVERVIEW
A high-performance Firefox extension that replaces your browser's User-Agent at the network level. By utilizing webRequest, it ensures web servers identify your browser and OS exactly as you choose, bypassing both client-side and server-side detection.

⚙️ HOW IT WORKS
Unlike scripts that only modify navigator.userAgent in JavaScript, this extension intercepts every outgoing HTTP request via webRequest.onBeforeSendHeaders. It rewrites headers before they leave your browser, providing a true network-level spoof that affects server-side logic and deep-packet inspection.

🆕 NEW IN VERSION 6.0: CHROMIUM HEADER INJECTION
To bypass modern anti-bot and fingerprinting systems (like Client Hints), the extension now dynamically injects five SEC-CH-UA headers when a Chromium-based UA is selected:

• Sec-Ch-Ua: Correct branding strings (e.g., "Google Chrome", "Chromium").
• Sec-Ch-Ua-Mobile: Accurate ?1 (mobile) or ?0 (desktop) flags.
• Sec-Ch-Ua-Platform: Matches the spoofed OS (Android, Windows, iOS, etc.).
• Sec-Ch-Ua-Platform-Version: Corresponding version strings.
• Sec-Ch-Ua-Full-Version-List: Precise build versioning.

🔹 Smart Logic:
• Brand Matching: Switches between Edge, Samsung, Opera, or Chrome brands based on active UA.
• Privacy Stripping: Firefox/Safari UAs have Client Hint headers stripped automatically.
• Accept Header Fix: Swaps Firefox’s format for Chrome’s on main_frame requests.

🌟 CORE FEATURES
• 50+ Preset User Agents across 9 categories.
• Dual Filtering Modes: Exclusion Mode and Inclusion Mode.
• "Always Real" Protection: Prevents breakage on cloudflare.com or 1.1.1.1.
• Intent Handling: Rewrites Android intent:// redirects into standard https:// URLs.
• Visual Feedback: Toolbar icon shows an "OFF" badge when inactive.

🛠️ USE CASES
• Bypass server-side blocks targeting specific browsers.
• Test responsive rendering without device-switching.
• Reduce your unique browser fingerprinting surface.
• Trigger mobile-optimized responses from desktop Firefox.