User Agent

User Agent Detector
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User Agent Detector

Analyze browser information, operating system details, and device type from user agent strings. Useful for web developers, testers, and security professionals.

Desktop
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Detecting your OS...
Loading user agent...

Test Custom User Agent

Common User Agent Examples (click to test):

Chrome on Windows Try
Safari on macOS Try
Safari on iPhone Try
Chrome on Android Try
Firefox on Windows Try

Understanding User Agents

What is a User Agent?

A user agent is a string of text that web browsers and other applications send to websites to identify themselves. It typically contains information about the browser, operating system, device, and other details that help websites deliver optimized content.

User Agent Format

The basic format of a modern user agent string is:

Mozilla/5.0 (platform; details) rendering_engine browser_name/version

For historical reasons, most browsers start with "Mozilla/5.0" regardless of their actual make.

Browser Information

The user agent contains specific browser details that help identify:

  • Browser name (Chrome, Firefox, Safari, Edge, etc.)
  • Browser version
  • Rendering engine (Blink, Gecko, WebKit, etc.)
  • Browser features and capabilities
Operating System Details

The operating system information typically includes:

  • OS name (Windows, macOS, Android, iOS, Linux)
  • OS version (Windows 10, macOS 11, Android 11)
  • Architecture (32-bit vs 64-bit, arm vs x86)
Device Information

On mobile devices, the user agent may include:

  • Device model (iPhone, Samsung SM-G998B, etc.)
  • Screen characteristics
  • Mobile-specific indicators
Why User Agents Matter
  • Feature Detection: Websites can serve different content based on browser capabilities
  • Responsive Design: Adapting layouts for different device types
  • Bug Tracking: Identifying browser-specific issues
  • Analytics: Understanding user demographics and technology usage
  • Security: Identifying potentially malicious requests
Limitations

User agent detection has some limitations:

  • User agents can be spoofed or modified
  • Browser extensions and privacy tools may alter them
  • Some browsers allow users to customize their user agent
  • Feature detection is generally more reliable than user agent sniffing
Best Practices

When working with user agents:

  • Use feature detection (e.g., Modernizr) instead of user agent sniffing when possible
  • Don't rely solely on user agent data for critical functionality
  • Consider the Client Hints API as a more modern alternative
  • Keep user agent parsing libraries updated as browser signatures change