Infer UA from its UA String

Usage no npm install needed!

<script type="module">
  import uainfer from '';



NPM version Build Status

This is a simple JavaScript library (MIT License) to infer the user agent from its claimed User-Agent string. The objective of uainfer to provide a human-friendly answer to the inquiry "What browser am I using?".

In the context of a web browser, the most common way to obtain the User-Agent string is from the value of navigator.userAgent. In the context of an HTTP server, it can be retrieved from the User-Agent header field in the HTTP request.

Example usage with Node.js REPL (or try it on RunKit):

> uainfer = require('uainfer');
> ua = uainfer.analyze('Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2)'
> ua.toString()
'Internet Explorer 7 on Windows XP'

(To use this library in a front-end application, see this JSFiddle demo)

For browsers utilizing Chrome/Blink engine (Samsung Browser, Opera, Vivaldi, etc), the result can contain the corresponding equivalent version of Chrome:

> console.log(ua)
UserAgent {
   { name: 'Vivaldi',
     version: 1.96,
     fullVersion: '1.96.1147.52',
     chromeFamily: { version: 65, fullVersion: '65.0.3325.183' } },
  os: { name: 'Windows', version: '10' } }


  • Recognize every single web browsers and obscure user agents out there.
  • Deduce other information such as CPU type, device, form factor, etc.

Design choices:

  • For a better maintenance, avoid regular expressions.
  • Always expand its small but fairly extensive test suite.
  • Keep it tidy and lightweight (4 KB when minified).

This library is created and maintained by @AriyaHidayat.