window.navigator.userAgent Redirect 1

Returns the user agent string for the current browser.

Syntax

var ua = window.navigator.userAgent;

Value

ua stores the user agent string value of the current browser.

The window.navigator.userAgent property is read-write; it has no default value.

The user agent string is built on a formal structure which can be decomposed into several pieces of info. Each of these pieces of info comes from other navigator properties which are also settable by the user. Gecko-based browsers comply with the following general structure:

userAgent = appCodeName/appVersion number (Platform; Security; OS-or-CPU; 
Localization; rv: revision-version-number) product/productSub 
Application-Name Application-Name-version

Example

alert(window.navigator.userAgent)
// alerts "Mozilla/5.0 (Windows; U; Win98; en-US; rv:0.9.2) Gecko/20010725 Netscape6/6.1"

Notes

Browser identification based on detecting the user agent string is unreliable and is not recommended, as the user agent string is user configurable. For example:

  • In Firefox, you can change the preference general.useragent.override in about:config. Some Firefox extensions do that; however, this only changes the HTTP header that gets sent, and doesn't affect browser detection performed by JavaScript code.
  • Opera 6+ allows users to set the browser identification string via a menu
  • Microsoft Internet Explorer uses the Windows registry
  • Safari and iCab allow users to change the browser user agent string to predefined Internet Explorer or Netscape strings via a menu.

Specifications

Specification Status Comment
WHATWG HTML Living Standard
The definition of 'NavigatorID.userAgent' in that specification.
Living Standard Initial definition

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)

 

See also

Document Tags and Contributors

 Last updated by: Sheppy,