What is my user agent?
Your user agent is the text your browser sends in the User-Agent header of every HTTP request, and scripts can read it as navigator.userAgent. The parser tool fills in your own browser's string automatically when the page loads; this guide uses one fixed Chrome on macOS string so the breakdown stays the same for every reader.
Worked example
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36
- Browser
- Chrome 120.0.0.0
- Engine
- Blink
- Operating system
- macOS 10.15.7
- Device class
- Desktop
- Device
- Unknown
- CPU architecture
- Unknown
- Bot / crawler
- No
Token breakdown
| Token | Interpretation |
|---|---|
| Mozilla/5.0 | A historical compatibility token. Almost every browser starts with it; it does not mean the browser is Firefox. |
| (Macintosh; Intel Mac OS X 10_15_7) | The platform comment. Chrome and Safari freeze the macOS version at 10_15_7, so newer macOS releases and Macs with Apple silicon send the same value. |
| AppleWebKit/537.36 | The engine token. Chrome's Blink engine began as a fork of WebKit and still reports this fixed value. |
| (KHTML, like Gecko) | A compatibility comment: WebKit descends from KHTML, and like Gecko was added for sites that only served modern pages to Gecko browsers. |
| Chrome/120.0.0.0 | The real browser and its version. Only the major version (120) is meaningful; Chrome sends 0.0.0 for minor, build and patch. |
| Safari/537.36 | Another compatibility token, so that sites looking for Safari treat Chrome as a WebKit-family browser. It does not mean the browser is Safari. |
The parser identifies Chrome 120 on macOS 10.15.7 with the Blink engine. Both the macOS version and the trailing 0.0.0 are frozen values, so the real system can be newer than the string says. CPU architecture stays unknown: the parser does not read Intel as a CPU hint, and Macs with Apple silicon send the same text.
Key rules
- A user agent string is a list of product/version tokens separated by spaces, with platform details in parentheses.
- Most tokens exist for compatibility: browsers copy each other's tokens so that older detection code keeps working, so a parser has to look at which tokens appear and in what order, not at single words.
- The parser tool fills in your own user agent from your browser when the page loads. The parsing itself runs in your browser, not on a server.
- Browser extensions, privacy settings, developer-tools device emulation and in-app browsers can change the user agent, so it may not describe the actual device.
- To compare browsers, paste a string from another device or choose a sample preset in the tool.