What does a user-agent string encode?
Every HTTP request from a browser includes a User-Agent header — a dense, historically-accumulated string like "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36" that packs in the browser engine, browser name and version, operating system, and device type. It reads oddly because browsers have spent two decades adding compatibility tokens (every browser claims to be "Mozilla") so that old sniffing scripts don't break — the useful signal is buried among legacy noise.
This tool parses that string and pulls out the browser, version, OS, device type, and rendering engine into a readable summary, so you don't have to eyeball the raw header.
When to use it
Use it when you're debugging a bug report that only happens on "some weird browser," and the reporter gave you their user-agent string instead of a browser name and version. It's also useful when reviewing server logs or analytics that log the raw UA header, when testing how your own site's UA-sniffing logic behaves against strings from browsers you don't have installed, or simply to check what your own browser reports (click Parse with an empty input to inspect your current one).
Keep in mind UA strings are increasingly "frozen" or reduced by browsers for privacy (Chrome's User-Agent Reduction, for instance), so modern strings carry less granular OS version detail than they used to — for precise feature detection, prefer client hints or feature-testing over UA parsing in production code.
Example
Paste "Mozilla/5.0 (iPhone; CPU iPhone OS 17_4 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.4 Mobile/15E148 Safari/604.1" and Parse resolves it to Browser: Safari 17.4, Operating System: iOS 17.4, Device Type: Mobile, Engine: WebKit — everything a support ticket needs, extracted from one dense line.
How to use the User-Agent Parser tool
- 1
Paste a user-agent string
Copy it from a bug report, server log, or browser dev tools.
- 2
Click Parse
Leave the field empty and click Parse to inspect your own browser's UA instead.
- 3
Read the breakdown
Browser, OS, device type, and rendering engine are shown as separate cards.
- 4
Share the result
Copy a permalink that restores the exact string you parsed, for including in a bug report or ticket.
Frequently asked questions
Is the string sent anywhere?
No — parsing runs entirely with local regular expressions in your browser; nothing is uploaded.
Why does it show "Unknown" for some fields?
The parser recognizes common patterns for major browsers (Chrome, Firefox, Safari, Edge, Opera) and OSes (Windows, macOS, iOS, Android, Linux). Uncommon or spoofed user agents, older browsers, or bots outside those patterns won't match and fall back to "Unknown".
Can a user-agent string be faked?
Yes, trivially — any client can send an arbitrary UA header, and browser extensions and dev tools let you override it. Treat UA-based detection as a hint for analytics or debugging, not as a security or access-control mechanism.
Why do all user agents start with "Mozilla/5.0"?
It's a historical compatibility token from the 1990s browser wars — sites once sniffed for "Mozilla" to serve richer pages, so every subsequent browser kept the prefix to avoid being excluded. It carries no meaningful information today.
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