The User Agent is a string that your browser sends to websites identifying itself, your operating system, and device type. It's one of the most basic but important fingerprinting vectors.
📋 User Agent Structure
A typical User Agent string looks like:
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36Breaking It Down
Mozilla/5.0- Historical compatibility tokenWindows NT 10.0; Win64; x64- Operating system infoAppleWebKit/537.36- Rendering engineChrome/120.0.0.0- Browser and versionSafari/537.36- Compatibility token
🔍 Information Revealed
| Information | Example |
|---|---|
| Browser | Chrome, Firefox, Safari, Edge |
| Browser Version | 120.0.0.0 |
| Operating System | Windows 10, macOS, Linux, Android, iOS |
| Architecture | x64, ARM, x86 |
| Device Type | Desktop, Mobile, Tablet |
🛡️ User Agent Spoofing
Antidetect browsers modify User Agent to:
- Match Profile: UA matches the spoofed OS and browser
- Stay Current: Use recent browser versions
- Be Consistent: UA matches other fingerprint parameters
- Avoid Detection: Use common, realistic combinations
🔄 User-Agent Client Hints
Modern browsers are moving to User-Agent Client Hints (UA-CH), which provide more structured information:
Sec-CH-UA: "Chromium";v="120", "Google Chrome";v="120"
Sec-CH-UA-Mobile: ?0
Sec-CH-UA-Platform: "Windows"Antidetect browsers must spoof both traditional UA and Client Hints for complete coverage.
❓ Frequently Asked Questions
Yes, browser extensions can change your UA. However, this alone isn't enough - your other fingerprints will still reveal your real browser and OS.
It's a historical artifact. Early websites served different content to Mozilla (Netscape). Other browsers added "Mozilla" to receive the same content. The practice stuck.