What Is a User Agent String?
A user agent string is a text identifier that your browser sends with every HTTP request to web servers. It tells the server what browser you are using, which operating system you are running, your device type, the rendering engine powering your browser, and your CPU architecture. This information is transmitted in the User-Agent HTTP header.
For example, a typical Chrome user agent on Windows looks like: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36. While this string looks complex, it contains structured information that our user agent checker parses into readable components.
Web developers and server administrators use user agent data for browser compatibility testing, serving optimized content, analytics, and debugging. You can inspect the full HTTP headers your browser sends — including the User-Agent header — with our HTTP Header Checker tool.
How User Agent Detection Works
Our user agent detection tool identifies your browser and system information through a simple four-step process that completes instantly:
Read the UA Header
When you visit this page, your browser automatically sends a User-Agent HTTP header with every request. Our server reads this header to get your raw user agent string.
Parse the String
The raw user agent string is parsed using pattern matching to extract structured data: browser name/version, OS, device type, rendering engine, and CPU architecture.
Identify Components
Each component is matched against a comprehensive database of known browsers, operating systems, devices, engines, and architectures to provide accurate identification.
Display Results
All detected information is displayed in organized cards. Your raw UA string is shown with a copy button. Use the custom parser to analyze any other user agent string.
Understanding User Agent String Components
When you check your user agent, our tool extracts and displays six key components from the UA string:
Browser
The web browser name (Chrome, Firefox, Safari, Edge, Opera, Brave) and its full version number. The major version is also extracted for quick reference.
Operating System
Your OS name and version — Windows 10/11, macOS Sonoma/Ventura, Linux, Android 14, iOS 17, Chrome OS. Helps developers optimize for specific platforms.
Device Type
Identifies whether you are on a desktop computer, mobile phone, or tablet. Also detects the device vendor (Apple, Samsung, Google) and model when available.
Rendering Engine
The layout engine that renders web pages: Blink (Chrome, Edge, Opera), WebKit (Safari), or Gecko (Firefox). Determines which CSS/HTML features are supported.
CPU Architecture
Your processor architecture: amd64 (Intel/AMD 64-bit), arm64 (Apple Silicon, ARM), arm (older mobile), ia32 (32-bit). Important for WebAssembly and native performance.
Raw String
The complete, unmodified user agent string as sent by your browser. Can be copied with one click for debugging, testing, or sharing with developers.
Common User Agent String Examples
Here are examples of real user agent strings from popular browsers and devices. You can paste any of these into the custom parser above to see how they are parsed:
Chrome on Windows
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36Safari on macOS
Mozilla/5.0 (Macintosh; Intel Mac OS X 14_2) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.2 Safari/605.1.15Firefox on Linux
Mozilla/5.0 (X11; Linux x86_64; rv:121.0) Gecko/20100101 Firefox/121.0Chrome on Android
Mozilla/5.0 (Linux; Android 14; Pixel 8) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.6099.144 Mobile Safari/537.36Safari on iPhone
Mozilla/5.0 (iPhone; CPU iPhone OS 17_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.2 Mobile/15E148 Safari/604.1Edge on Windows
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36 Edg/120.0.0.0
Why Check Your User Agent?
There are many practical reasons to check your user agent or analyze a user agent string:
Web Development & Testing
Verify how your browser identifies itself when testing responsive designs, browser-specific CSS, or feature detection. Compare UA strings across browsers and devices.
Debugging Website Issues
When a website doesn't work correctly, checking your user agent helps identify if the site is serving wrong content based on browser detection or UA sniffing.
Privacy & Fingerprinting
Check what information your browser reveals to websites. Your user agent is one of the signals used in browser fingerprinting to track you across the web.
Bot & Crawler Detection
Analyze user agent strings from your server logs to identify search engine crawlers (Googlebot, Bingbot), social media bots, or potentially malicious scrapers.
Device Compatibility
Confirm your browser and OS version when troubleshooting compatibility issues, checking system requirements, or verifying that a browser extension changed your UA.
Analytics & Reporting
Understand the user agent strings in your web analytics data. Identify which browsers, OS versions, and device types your visitors use most frequently.
User Agent and Browser Fingerprinting
Your user agent string is one of many signals that websites can use to create a browser fingerprint — a nearly unique identifier for your browser. While a user agent alone is not unique enough to identify you, combined with other data points it contributes to a digital fingerprint.
What Your UA Reveals
- Browser name, version, and major release
- Operating system and exact version
- Device type (desktop, mobile, tablet)
- CPU architecture (amd64, arm64)
- Rendering engine and version
- Language and platform preferences
Reducing Your Fingerprint
- Use Firefox or Brave with anti-fingerprinting enabled
- Enable resistFingerprinting in Firefox (about:config)
- Use Tor Browser for maximum anonymity
- Avoid installing unique browser extensions
- Use standard screen resolutions and system fonts
- Consider User-Agent Client Hints reduction
Browsers are gradually reducing the information in user agent strings. Chrome's User-Agent Reduction initiative freezes parts of the UA string to reduce passive fingerprinting. The HTTP Headers tool lets you inspect all headers your browser sends, including privacy-related ones like Sec-CH-UA Client Hints.
User Agent in Web Development
Understanding user agents is essential for web development. Here are three key approaches to working with user agent data:
Feature Detection
The modern best practice. Instead of checking user agent strings, test for specific browser capabilities using JavaScript APIs. For example, check for 'IntersectionObserver' in window rather than parsing the UA for Chrome 58+. Libraries like Modernizr automate this.
Server-Side UA Parsing
Parse user agent strings on the server to serve optimized content. Useful for serving different image formats (WebP vs JPEG), pre-rendering for crawlers, or redirecting mobile users. Libraries like ua-parser-js (used by this tool) make server-side parsing reliable.
Client Hints API
The future of user agent detection. Servers request specific information via Accept-CH header, and browsers respond with structured headers like Sec-CH-UA-Platform and Sec-CH-UA-Mobile. More privacy-friendly than traditional UA strings. Supported in Chromium-based browsers.
Related Network & Utility Tools
Complement your user agent check with these free tools for network diagnostics and web analysis:
Inspect all HTTP response headers including security headers and content negotiation.
Detect your public IPv4 and IPv6 addresses with geolocation and ISP details.
Identify your Internet Service Provider, ASN, and connection details.
Verify SSL certificate validity, expiration, and security configuration of any website.
Check all DNS records (A, AAAA, CNAME, MX, NS, TXT) for any domain name.
Look up detailed information for any IP address including geolocation and ASN.
Generate strong, random passwords with customizable length and character types.
Create QR codes for URLs, text, WiFi, vCards, and more with customization options.
Frequently Asked Questions About User Agents
What is my user agent?
Your user agent is a text string your browser sends with every HTTP request. It identifies your browser name/version, OS, device type, rendering engine, and CPU. This page auto-detects your user agent string and parses it into readable components.
What's my user agent string used for?
Servers use it to serve optimized content — different layouts for mobile vs desktop, correct file formats (WebP vs JPEG), analytics tracking, and browser compatibility. It's sent automatically in the User-Agent HTTP header with every request.
How do I find my user agent?
Visit this page for instant auto-detection. Alternatively, open DevTools (F12) → Console → type navigator.userAgent. Or check the Network tab in DevTools and look at the User-Agent header in any request.
Can I change my user agent?
Yes — use DevTools to override it temporarily, install a User-Agent Switcher extension, or configure it in browser settings. Developers change UAs to test how sites respond to different browsers and devices.
What is a rendering engine?
It's the software that transforms HTML/CSS/JS into the visual page you see. Main engines: Blink (Chrome, Edge, Opera), WebKit (Safari), Gecko (Firefox). Your user agent string includes the engine name and version.
Why do all user agents start with Mozilla/5.0?
Historical compatibility. Early servers checked for 'Mozilla' to serve advanced content. Other browsers added it to avoid receiving basic pages. This legacy prefix persists today even though it's meaningless.
Can websites track me using my user agent?
Your UA alone isn't unique, but it contributes to browser fingerprinting when combined with screen size, fonts, timezone, and other signals. Use Firefox/Brave with anti-fingerprinting or Tor Browser to reduce tracking.
What are Client Hints?
User-Agent Client Hints (UA-CH) is a newer API providing browser info in a structured, privacy-friendly way. Instead of sending all details in every request, servers request only what they need. Supported in Chrome and Edge.
What's the difference between user agent and user agent string?
A 'user agent' is the software (your browser) acting on your behalf. The 'user agent string' is the text identifier it sends to servers. In practice, both terms are used interchangeably.
Is this user agent checker free and safe?
Yes, 100% free with no registration. We read your browser's User-Agent header (sent to every site you visit) and parse it. We don't store, log, or share your data.