What is a User-Agent
A User-Agent is a string by which a browser, an app or a bot introduces itself to a server in every request. It contains the browser name and version, the engine, the operating system and the device type. Sites use it to decide which version of a page to show, mobile or desktop, and whether to let a bot in.
What a User-Agent consists of
- Mozilla/5.0 — a historical prefix present in almost every string for compatibility.
- Platform in brackets — the operating system and device, for example Windows NT 10.0 or Android 14.
- Engine — AppleWebKit, Gecko or Chrome with a version number.
- Browser and version — Chrome, Firefox, Safari, Edge and others, sometimes at the end of the string.
- The Mobile token — a sign of a smartphone. Without it an Android device is considered a tablet.
User-Agents of search and other bots
Can you trust a User-Agent
No: the string is sent by the client itself, and anyone can fake it. So a User-Agent must not be used to grant access or to treat a visitor as a real search bot. The authenticity of Googlebot is checked by IP address in Googlebot Checker, and the headers the server sends in response are shown by HTTP Headers Checker. You can find your own IP address on the neighbouring page.
How to change a User-Agent
In Chrome and Edge open developer tools, the three-dot menu, More tools, Network conditions and clear Use browser default. There you can pick the User-Agent of Googlebot or a smartphone to see how the site responds to a bot. In Firefox and Safari there are extensions or a developer mode for this. For quick checks it is more convenient to use online tools from our server.
Why the User-Agent is becoming less informative
Browsers are gradually freezing the User-Agent string: the OS version and the browser’s minor version in it no longer change. Instead Client Hints appear, which a site has to request separately. So, for example, Windows 11 still looks like Windows 10 in the string, and in macOS the version is always 10.15.7. This is normal, not a parsing error.
What else StayIndexed can do
This page is a free tool from the StayIndexed service. User-Agent parsing works right in your browser, and in your account you can track how your pages are doing in Google: indexing, speed, redirects, headers and Googlebot access.
How much it costs
The check is free, both on this page and in your account. Tokens are used to pay for the other services: indexing, speed and backlinks cost 3 tokens per check. 30 tokens are credited at sign-up, no card required.
Frequently asked questions
What is a User-Agent?
It is a string by which a browser or bot introduces itself to a server in every request: the browser name and version, the engine, the operating system and the device type.
How do I find my User-Agent?
It is shown on this page right after it opens: we read it in your browser and break it down into browser, system and device. You can copy it with the button under the string.
How do I parse a User-Agent from server logs?
Paste the string into the field above and press the Parse button: we will show the browser, system, device and engine and determine whether it is a known bot.
How do I tell the real Googlebot from a fake?
You cannot by User-Agent: it gets faked. Check the visitor’s IP address with reverse DNS or against Google’s ranges, for example in Googlebot Checker.
Why does a User-Agent always say Mozilla?
It is a legacy of the 1990s: the first browsers posed as Mozilla so that sites would serve them modern pages. Since then the prefix has stayed in every browser for compatibility.
Do you store my User-Agent?
No. The parsing runs in your browser, and we send nothing to the server.