User-agent parser
Paste any user-agent string and this breaks it into browser, version, layout engine, operating system and device. Leave the box as it is to read your own. When it is your browser, the client-hint values appear beside the string so you can see where a frozen OS token is reduction, not a lie. It all runs in your browser.
Nothing is sent. Parsing happens on your machine. This is a pragmatic parser for the common browsers and systems, not an exhaustive database; an unusual string may parse partially.
Browser, engine, system, device
A user-agent string is a compact, messy history of the web: every browser still claims to be “Mozilla”, and most claim to be several engines at once. The parser pulls out the parts that actually identify your browser today and ignores the legacy tokens.
Why your OS version looks frozen
Chrome deliberately freezes parts of the user-agent — the OS version, the minor browser version — and moves the real values into User-Agent Client Hints, which a site must ask for. So a Windows 11 machine still says “Windows NT 10.0” in the string, with the true version in Sec-CH-UA-Platform-Version. That is reduction, and the parser explains it rather than flagging it. A real contradiction is when the string and the hints name a different browser or platform — the mark of a user-agent switcher. Mosaic draws the string and the hints together from one real device, so they agree.
- Paste a user-agent. Paste any user-agent string, or leave the box to read your own. Parsing runs in your browser; nothing is sent.
- Read the breakdown. The tool splits the string into browser and version, layout engine, operating system and device type.
- See the client hints. For your own browser it shows the client-hint values beside the string and explains where a frozen OS token is reduction, not a lie.
What is a user-agent string?
A line your browser sends with every request naming the browser, its version, the layout engine and the operating system. Sites use it to tailor pages and to tell browsers apart.
Why does my user-agent say Windows 10 when I am on Windows 11?
That is user-agent reduction, not a lie: Chrome freezes the OS token at “Windows NT 10.0” and moves the real version into client hints (Sec-CH-UA-Platform-Version). The parser shows the client-hint value beside the string and explains the difference rather than flagging it.
What counts as a real contradiction?
When the user-agent and the client hints disagree in a way reduction does not explain — a different browser brand or platform — which is what a UA-switcher extension produces and a detector reads. Mosaic draws the string and the hints together from a real device, so they agree.
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