What is a User Agent Parser?
Every browser sends a user agent string with each request, a compact, oddly formatted piece of text that identifies the browser, its version, the operating system, and the device type. It looks like line noise at first glance ("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36..."), a historical artifact from decades of browsers each adding their own compatibility tokens on top of each other. This tool parses that string and tells you, in plain language, exactly what browser, OS, and device it actually describes.
When to use it
The most common reason to reach for this is simply checking your own user agent, what does my browser actually report itself as? This tool detects and parses your current browser's user agent automatically the moment you open it, so you don't need to dig it out of developer tools yourself. Beyond that, developers use this when debugging browser-specific bugs (confirming which exact browser and version a bug report came from), analyzing server logs that show raw user agent strings instead of friendly names, or checking how a specific user agent string will be categorized by browser-detection code before shipping it.
How it works
Parsing a user agent string is pattern matching, not a lookup against some official registry, there's no single authoritative source, because user agent strings were never a strictly standardized format. This tool checks the string against known patterns for major browsers (checking for more specific engines like Edge and Opera before falling back to the more generic Chrome pattern their user agents also contain, since both are built on Chromium and include "Chrome" in their string), operating systems, and device-type indicators like "Mobile" or "iPad" tokens, in an order designed to catch the specific cases before the general ones.
Frequently asked questions
What is my user agent, and why does my browser send it?
Your user agent is a text string your browser automatically includes with every request, identifying itself, its version, and your operating system. Websites use it to serve appropriate content (like a mobile-optimized layout) or for analytics, this tool shows you exactly what your browser is currently reporting, detected automatically when you open it.
Why does an Edge or Opera user agent also contain the word 'Chrome'?
Edge, Opera, and several other browsers are built on the Chromium engine, the same open-source project Chrome is built on, so their user agent strings include Chrome-identifying tokens for compatibility with sites that check for it. Accurate detection has to check for the more specific browser-identifying tokens (like "Edg/" or "OPR/") before falling back to a generic Chrome match, or it will misidentify Edge and Opera as Chrome.
Can a website's user agent detection be spoofed or inaccurate?
Yes, a user agent string is just a value the browser chooses to send, and browser developer tools let anyone override it to whatever value they want, for testing responsive designs or bypassing basic browser checks. User agent detection should be treated as a best-effort hint about the client, not a guaranteed or tamper-proof fact.
Is checking the user agent the reliable way to detect mobile devices?
It's a common approach but not the most reliable one, modern best practice favors feature detection (checking whether a specific capability like touch input exists) or CSS media queries over parsing the user agent string, since user agents can be spoofed, are inconsistently formatted across browsers, and change over time as browsers update.