What is my user agent?
The line above is what your browser announces to every server it talks to. It names a rendering engine, a platform and a version, and most of it is compatibility theatre kept from the 1990s browser wars. Treat it as a claim rather than a measurement: it is trivially editable, and modern browsers deliberately report less of it than they used to.
Your user agent is a single line of text your browser attaches to every request it makes. It is meant to tell a server which browser, rendering engine and operating system it is talking to, so the server can send back a page that works. Yours is shown in full above, exactly as a web server receives it.
A modern user agent looks like a small archaeological dig. It usually starts with "Mozilla/5.0" for historical reasons that have nothing to do with Mozilla, then lists platform tokens like "Windows NT 10.0" or "Macintosh", then the engine ("AppleWebKit", "Gecko"), and finally the browser and version. Chrome, Edge and Opera all still claim to be "like Gecko" and "Safari" because sites once sniffed for those names.
Because so many products cram compatibility tokens into the string, the user agent is more of a compatibility flag than a clean fact sheet. That is also why it is only a hint, not proof: any client can send any string it likes.
How a website reads this
This is the exact call a page makes. Nothing else is involved, and nothing is sent anywhere: the value is read in your browser and displayed to you.
navigator.userAgentReturns one string, always. There is no browser setting that makes it empty, because the same string also travels as the User-Agent request header on every request the browser makes.
- Needs your permission
- No, it is read silently
- Can it be faked
- Yes. It is a plain header. An extension, the devtools device toolbar or any HTTP client can send whatever it likes, and no site can verify it.
- Contribution to a fingerprint
- About 10 bits, our own estimate. Our estimate, on the reasoning that the string carries browser, major version, platform and architecture in one field. Chrome's User-Agent Reduction has been shrinking this since 2022. How we estimate this.
What each browser does with it
The same call does not give the same answer everywhere. Several browsers withhold, round or cap this value on purpose, so a blank or suspiciously round result is usually a privacy decision rather than a fault.
| Browser | What it reports |
|---|---|
| Chrome and other Chromium browsers | Reduced string: minor version digits report as zeros and the platform detail is flattened. Full detail moved to Client Hints, which a site has to ask for. |
| Firefox | Rounded version. With resistFingerprinting on, reports a generic string shared by all users of that mode. |
| Safari | Frozen platform tokens and a coarse version. Safari has reported a near-static string for years. |
| Tor Browser | One identical string for every user on that platform, by design. Standing out is the thing it is avoiding. |
What you should know
Why sites collect it
Servers read the user agent to pick a layout, serve the right download, warn about unsupported browsers, gather rough analytics on which browsers visitors use, and block obvious bots. Advertisers and fingerprinting scripts fold it into a device profile because the exact version numbers narrow down who you are.
Privacy implications
On its own a user agent rarely identifies you, but it is one of the most reused fingerprinting signals because it carries browser, version and OS in one string. Combined with your screen size, timezone and fonts it becomes far more revealing. Browsers have started freezing or trimming the string (Chrome's User-Agent Reduction) precisely to blunt this.
How to change or hide it
You can change your user agent per site with an extension, or globally in a browser's developer tools under the device toolbar. Some privacy browsers (Tor Browser, Brave) deliberately send a common, generic string so you blend in with everyone else. Spoofing it can break sites that branch on it, so test before you rely on it.
Frequently asked questions
Is a user agent unique to me?
Usually not by itself, since millions of people run the same browser version on the same OS. It becomes identifying when combined with other signals like screen size, timezone and installed fonts.
Can I fake my user agent?
Yes. It is just a request header, so an extension or your browser's dev tools can send any value. Sites cannot verify it, though some behaviour checks can catch obvious mismatches.
Why does Chrome's user agent mention Safari and Gecko?
For backward compatibility. Years ago sites checked for those names to enable modern features, so every browser kept the tokens to avoid being served a worse page.
Sources
Browser behaviour changes and vendors cap these values differently, so the claims above that are not self-evident are checked against the specifications and vendor documentation below.
Last checked on . How these values are measured and estimated is set out on the methodology page.
Something wrong here? Tell us what your browser reports and it gets corrected.