Web guide
How to use a user agent parser
A user agent parser extracts recognizable browser, operating-system, device, or bot tokens from a request header. Its output is a best-effort interpretation, not verified identity.
Open the User Agent ParserParse a user-agent string
- Paste the complete user-agent string or select Use this browser.
- Select Parse user agent.
- Review the detected browser, version, operating system, and device category.
- Treat unknown or ambiguous fields as normal.
- Copy the result only as diagnostic context.
The free user agent parser processes the string locally and accepts up to 4,096 characters.
Why the string looks complicated
User-agent strings accumulated compatibility tokens over many years. A modern browser can mention Mozilla, AppleWebKit, Chrome, Safari, and its own product token in one line. Parsers therefore use ordered heuristics rather than simply choosing the first familiar name.
Key rule: a token is a clue. The full token pattern and order determine the likely interpretation.
What a parser can and cannot infer
| Possible clue | Important limitation |
|---|---|
| Browser family and version | Strings can be reduced, frozen, or spoofed |
| Operating-system family | Tokens may map several releases to one value |
| Mobile or desktop category | Desktop mode and embedded browsers can blur the distinction |
| Known crawler token | A name such as Googlebot does not prove the requester is genuine |
Common ambiguous cases
- Chrome-compatible browsers often include Chrome and Safari compatibility tokens.
- Windows NT 10.0 does not reliably distinguish Windows 10 from later Windows versions.
- An iPad requesting a desktop site can resemble a Mac.
- An embedded web view may resemble the browser engine it uses.
- Bot strings can be copied by any client.
Do not use user agents as capability tests
For web compatibility decisions, test whether the required API or behavior exists. Feature detection is more reliable than assuming every browser with a certain label behaves identically. On the server, user-agent parsing can support analytics or broad content choices, but keep a safe default for unknown clients.