User Agent Parser
Parse any User-Agent string to identify browser, OS, device type and version information.
| Browser | Unknown |
| Operating system | Unknown |
| Device type | Bot/Crawler |
| Rendering engine | WebKit |
About User-Agent Strings
The User-Agent (UA) string is a header sent with every HTTP request that identifies the browser, rendering engine, operating system, and device making the request. Web servers and analytics tools use it to tailor responses, log visitor demographics, or detect bots and crawlers.
User-Agent string anatomy
A typical Chrome UA string looks like:
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36
The string contains historical legacy tokens (Mozilla/5.0 is present in virtually all browsers for compatibility reasons, even non-Mozilla browsers), followed by platform information in parentheses, then the rendering engine and browser version.
Common use cases for UA parsing
- Analytics — Understanding what browsers and devices your visitors use
- Bot detection — Identifying search engine crawlers (Googlebot, Bingbot), monitoring services, and malicious scrapers
- Feature detection fallback — Some legacy compatibility decisions still require UA sniffing when feature detection is insufficient
- Debugging — Reproducing issues reported by users on specific platforms
UA spoofing and limitations
User-Agent strings can be freely modified by users, browsers, and tools. A bot can claim to be Chrome on Windows; a developer can change their browser's UA for testing. UA strings should be used as heuristics, not as reliable identification. Modern privacy initiatives (like reduced UA strings in Chrome) are progressively removing device and OS version detail from UAs.