Result
Paste a user-agent string above — your own browser's is filled in automatically when the page loads.
Parsing happens entirely in your browser; nothing you paste here is sent anywhere. A user-agent is a self-declaration — this shows what the string claims, which is not proof of what actually sent it.
Why every browser claims to be Mozilla
User-agent strings are a fossil record. In the 1990s, sites served better pages to Netscape ("Mozilla"), so Internet Explorer declared itself Mozilla-compatible; every browser since has kept the prefix, then added its own layer of compatibility claims. That is why today's Chrome says Mozilla/5.0, AppleWebKit, KHTML, like Gecko and Safari — four other browsers' names — before its own. Parsing one correctly means checking the most specific tokens first, which is exactly what this tool does.
User agents and automation
HTTP libraries announce themselves by default — python-requests/2.31.0, curl/8.6.0, Go-http-client/2.0 — and sites that filter automated traffic check this header first, before they ever look at your IP. If you are debugging why a scraper is treated differently from a browser, compare the user agent it sends against the one your browser sends: you can see both on the What Is My IP page, which shows every header your client transmits.
What a UA string cannot tell you
The header is freely chosen by the client, so it proves nothing on its own: a script can send a perfect Chrome string, and some privacy tools deliberately blur theirs. There are also honest ambiguities — Windows 11 still reports Windows NT 10.0, and iPads on iPadOS 13+ describe themselves as Macs. Where the string genuinely cannot distinguish, this parser says so rather than picking a side.