What is a user agent string?
A user agent string is a text identifier that your browser sends to every website you visit. It contains information about your browser name and version, operating system, device type, and rendering engine. Web servers use this information to deliver optimised content — for example, serving a mobile layout to smartphones or enabling specific features for modern browsers.
Why parse user agents?
Developers and QA engineers parse user agent strings to debug browser-specific issues, analyse traffic patterns, and ensure compatibility across devices. SEO professionals check user agents to understand how search engine crawlers (like Googlebot) see their pages. This tool parses user agent strings entirely in your browser using pattern matching — no data is sent to any server.
Limitations
User agent strings can be spoofed or modified by browser extensions. Some modern browsers are moving towards reduced user agent strings for privacy. This parser uses common patterns and may not identify every possible browser or device variant.