What is my user agent?

Your browser sends this line to every site it opens. Below: what each part of it means and what else your browser tells sites about itself.

Your user agent

Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)

Check another user agent

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Parsed in your browser. What you paste isn't sent anywhere.

What is a user agent?

A user agent is a line of text your browser sends to every site with each request, in the User-Agent header. Scripts on a page can read it too, as navigator.userAgent. It names the browser and its version, the engine, the operating system and, on some phones, the model. Sites use it to pick the right version of a page, to count which browsers their visitors use and to tell people from bots.

How to read a user agent string

Here is the user agent of Chrome on Windows:

Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/141.0.0.0 Safari/537.36

Mozilla/5.0: sent by almost every browser for compatibility with old sites. It doesn't mean Firefox.
(Windows NT 10.0; Win64; x64): the system, 64-bit Windows 10 or 11.
AppleWebKit/537.36 (KHTML, like Gecko): the engine. Chrome's engine, Blink, grew out of WebKit, and Chrome still names it.
Chrome/141.0.0.0: the browser and its version.
Safari/537.36: added for sites that look for Safari. It isn't Safari.

Firefox sends a shorter line with its own engine, Gecko:

Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:143.0) Gecko/20100101 Firefox/143.0

Why the user agent says Windows 10 on Windows 11

Browsers have stopped putting some exact details into the user agent, so that fewer people can be told apart by it. These parts stay the same whatever you have:

Windows NT 10.0 on both Windows 10 and Windows 11;
Mac OS X 10_15_7 on newer macOS versions, and «Intel» on Macs with Apple chips;
Android 10; K in Chrome instead of the Android version and the phone model;
zeros after the first number of Chrome's version, as in Chrome/141.0.0.0;
iPhone OS 18_6 or a similar older number in Safari on iOS 26 and newer.

The exact values are in Client Hints, which only Chrome-based browsers have. When your browser has them, this page shows them above.

What are User-Agent Client Hints?

Client Hints are a newer way for sites to learn about the browser. Chrome, Edge, Opera and other Chrome-based browsers send three short headers to every HTTPS site: Sec-CH-UA with browser names and versions, Sec-CH-UA-Mobile with whether it's a phone and Sec-CH-UA-Platform with the system. A site can ask for more, such as the exact system version, the processor architecture or the phone model: with the Accept-CH header or with navigator.userAgentData.getHighEntropyValues() in JavaScript. Firefox and Safari don't send Client Hints.

The list of names may include a made-up one like Not)A;Brand: Chrome adds it on purpose, so that sites don't rely on exact names.

How to change your user agent

Chrome and Edge: open developer tools (F12), then the ⋮ menu → More tools → Network conditions, and turn off «Use browser default» next to User agent. It works in that tab while developer tools are open.
Firefox: type about:config in the address bar and add the setting general.useragent.override with the new line.
Safari on Mac: turn on the features for web developers in Settings → Advanced, then choose Develop → User Agent.

A user agent changed on its own is easy to spot. Sites also see the browser's engine, Client Hints, the system's fonts and the screen: when the user agent says Safari on iPhone and the rest says Chrome on Windows, the site sees that they don't match.

FAQ

Can a site see my user agent?

Yes: the browser sends it with every request, and scripts on a page can read it as navigator.userAgent.

Is my user agent unique?

No: everyone with the same browser version on the same system sends the same line. Sites combine it with other details, such as the screen, fonts and time zone, to tell browsers apart.

Why does Chrome's user agent say Mozilla and Safari?

Old sites gave their full versions only to browsers they knew. New browsers added the names of older ones to get them, and Chrome keeps Mozilla, AppleWebKit and Safari for compatibility.

Why does my Mac with an Apple chip say Intel?

Safari, Chrome and Firefox write «Intel Mac OS X» on every Mac, so the user agent doesn't tell Apple chips from Intel ones. Chrome-based browsers give the real architecture in Client Hints.

Does a VPN or proxy change my user agent?

No. A VPN or proxy changes the IP address sites see; the user agent comes from your browser.

What does the user agent of a bot look like?

Search engine crawlers name themselves, like Googlebot/2.1 or bingbot/2.0, often with a link to a page about the bot. Scripts send the name of their library, like curl/8.7.1 or python-requests/2.32.3, unless the author puts in a browser's user agent. Paste one into the field above to check.