User Agent Parser

Free online tool. All processing is client-side. No signup needed.

How to Use the User Agent Parser

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What is a User Agent Parser?

A User-Agent Parser decodes the cryptic User-Agent strings that browsers and bots send with every HTTP request into human-readable information: browser name and version, operating system, device type (mobile/tablet/desktop), rendering engine, and bot identification. User-Agent parsing is essential for web analytics, server-side rendering decisions, security bot detection, and understanding your website's audience. The string 'Mozilla/5.0 (iPhone; CPU iPhone OS 18_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Mobile/15E148 Safari/604.1' tells a rich story — this parser translates it instantly.

How Does It Work?

Paste any User-Agent string and the parser breaks it down into: Browser (Chrome 125, Safari 18, Firefox 126), OS (Windows 11, macOS 15, iOS 18, Android 15), Device (iPhone 15 Pro, Samsung Galaxy S25, MacBook Pro), Engine (Blink, WebKit, Gecko), and Bot/Crawler detection (Googlebot, Bingbot, etc.). The parser uses a regularly updated UA database, handling the backward-compatibility artifacts that make all modern User-Agents start with 'Mozilla/5.0' (a 20-year-old browser wars artifact).

Formula

User-Agent Structure:\nMozilla/5.0 ([system info]) [platform details] [engine info] [app details]\n\nComponents:\n• Browser: Safari/604.1, Chrome/125.0.0, Firefox/126.0\n• OS: Windows NT 10.0 (Win10/11), Mac OS X 10_15_7 (macOS), X11; Linux\n• Mobile: iPhone (iOS), Android + model info\n• Engine: AppleWebKit (Safari), Gecko (Firefox), Blink (Chrome)\n\nBot Identification:\n• Googlebot, Bingbot, YandexBot, Baiduspider\n• AhrefsBot, SemrushBot (SEO tools)\n• UptimeRobot, Pingdom (monitoring)\n\nWhy all UAs start with 'Mozilla/5.0': historical compatibility — browsers that didn't claim to be Mozilla were blocked from JavaScript-heavy sites in the 1990s

Who Uses This Tool?

Web developers debugging browser-specific issues by checking UA details
Analytics engineers parsing server logs for browser/OS market share
Security engineers detecting bots, scrapers, and malicious requests
SEO specialists verifying crawler User-Agents in access logs
Marketers understanding device breakdown of website visitors

Pro Tips

Don't rely on User-Agent for critical logic — it's easily spoofed. Use feature detection (e.g., 'does this browser support WebP?') instead of UA sniffing
User-Agent Client Hints (UA-CH) is the modern replacement: browsers send structured headers (Sec-CH-UA, Sec-CH-UA-Platform) instead of a monolithic UA string. Our parser supports both
For bot detection, combine UA parsing with reverse DNS lookup and behavior analysis. Many malicious bots impersonate Chrome or Googlebot
Mobile detection: UA parsing with device lookup tables is the most accurate method. CSS media queries and screen.width detect screen size, not device type (a desktop can have a small window)

Frequently Asked Questions about User Agent Parser

Why does every User-Agent start with 'Mozilla/5.0'?

Backward compatibility from the 1990s browser wars. Websites used to block non-Netscape (Mozilla) browsers. Internet Explorer, then Chrome/Safari/Firefox, all included 'Mozilla' to avoid being blocked. The '5.0' version has been frozen since 2006.

Can I detect bots using User-Agent?

Some bots use recognizable UA strings (Googlebot, Bingbot). However, many malicious bots impersonate real browsers. Use UA filtering as one signal among many (behavioral analysis, IP reputation, CAPTCHA, reverse DNS).

Free online User Agent Parser — no signup, 100% client-side processing. All data stays in your browser.