How it works
The User Agent Parser decodes a user agent string — the browser identification string sent in every HTTP request — into its components: browser name and version, rendering engine, operating system, device type, and CPU architecture.
User agent strings are the primary way web servers identify clients. They're used for browser compatibility decisions, analytics (which browsers do your users use?), bot detection (is this a real user or a crawler?), responsive serving (serve different assets to mobile vs. desktop), and content negotiation. But the strings are notoriously complex and inconsistent — this parser handles the edge cases.
How to use it: your current user agent is auto-detected and displayed. Paste any user agent string in the input field to parse it. The parsed result shows each component separately: browser name, version, engine (Blink, Gecko, WebKit), OS name, OS version, device type (desktop/tablet/mobile), device manufacturer and model (for mobile), and whether it's a bot.
User agent examples: - Chrome on Windows: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36 - iPhone Safari: Mozilla/5.0 (iPhone; CPU iPhone OS 17_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.0 Mobile/15E148 Safari/604.1 - Googlebot: Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
Bot detection: the parser identifies common crawler and bot user agents — Googlebot, Bingbot, Slurp, DuckDuckBot, Baiduspider, YandexBot, and many others — which is useful for filtering crawlers out of analytics data.
Frequently Asked Questions
- Historical compatibility. When Netscape (Mozilla) and Internet Explorer were dominant, websites served different content to each. Later browsers adopted 'Mozilla/5.0' to avoid being served degraded content. The pattern persisted — every major browser today claims to be 'Mozilla/5.0' for historical compatibility reasons.
- Yes. Any browser can send any user agent string. Privacy-focused browsers may randomize or simplify their UA string. Request-forging tools can send any UA they want. Do not use user agents for security decisions — only for analytics and progressive enhancement.
- The parser identifies Googlebot user agents (Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)). For production bot detection, also verify the IP reverse-DNS lookup against google.com — anyone can spoof the UA string.
- KHTML is the rendering engine that Apple forked to create WebKit (Safari's engine). 'Like Gecko' was added for Gecko (Firefox) compatibility. Apple added 'Chrome' to Safari's UA to avoid being served Firefox-only content. This UA string complexity is entirely historical compatibility theater.