What is a user agent?
Every time your browser loads a page, it sends a User-Agent header — a line of text naming the browser, its version, the rendering engine and the operating system. Websites use it to serve compatible pages, show the right download button, and count which browsers visitors use.
Reading a user agent string
A typical Chrome on Windows string looks like this:
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/142.0.0.0 Safari/537.36| Part | Meaning |
|---|---|
Mozilla/5.0 | Historical compatibility token — sent by almost every browser |
(Windows NT 10.0; Win64; x64) | Operating system and CPU architecture |
AppleWebKit/537.36 (KHTML, like Gecko) | Rendering engine compatibility tokens |
Chrome/142.0.0.0 | The actual browser and version |
Safari/537.36 | Another compatibility token |
Why the details look odd
Browsers have copied each other’s tokens for decades so sites don’t block them — which is why Chrome mentions Safari and every browser says “Mozilla”. Modern browsers also freeze parts of the string for privacy: Windows 11 still reports “Windows NT 10.0”, macOS versions are capped, and Chrome reduces minor version numbers. Where supported, this tool uses User-Agent Client Hints to get more accurate details, such as distinguishing Windows 11.
When do you need your user agent?
- Reporting a website bug to support or a developer.
- Checking which browser version you’re actually running.
- Testing or configuring analytics, bot rules or responsive designs.
Also see your public address with What is my IP.
Frequently asked questions
What is my user agent?
It’s shown in full above, along with the browser, operating system and device it describes.
Why does my user agent say Windows 10 on Windows 11?
Browsers froze the Windows version in the user agent. Client Hints, used here when available, report Windows 11 correctly.
Can I change my user agent?
Yes — browser developer tools and extensions can override it, mainly for testing.
Can websites identify me from my user agent?
Not on its own, but combined with other details it can contribute to browser fingerprinting.