Returns the version of the browser as a string. It may be either a plain version number, like "5.0", or a version number followed by more detailed information. The HTML5 specification also allows any browser to return "4.0" here, for compatibility reasons.
veris the version number of the browser as a string.
alert("Your browser version is reported as " + navigator.appVersion);
window.navigator.userAgent property may also contain the version number (example: "
Mozilla/5.0 (Windows; U; Win98; en-US; rv:0.9.2) Gecko/20010725 Netscape 6/6.1"), but you should be aware of how easy it is to change the user agent string and "spoof" other browsers, platforms, or user agents, and also how cavalier the browser vendor themselves are with these properties.
window.navigator.userAgent properties have been used in "browser sniffing" code: scripts that attempt to find out what kind of browser you are using and adjust pages accordingly. This lead to the current situation, where browsers had to return fake values from these properties in order not to be locked out of some websites.
This was originally part of DOM Level 0, but has been since included in the HTML5 spec.