About URI Scheme

About URI Scheme

about is an internal URI scheme (also known as a “URL scheme” or, erroneously, “protocol”) implemented in various Web browsers to reveal internal state and built-in functions. It is an IANA officially registered scheme, and is standardised.

In early versions of Netscape, any URI beginning about: which wasn't recognised as a built-in command would simply result in the text after the colon being displayed. Similarly, in early versions of Internet Explorer, about: followed by a string of HTML (e.g. about:hello world) would render that string as though it were the source of the page — thus providing a similar (though more limited) facility to the data: URI scheme defined by RFC 2397. Still other versions of Netscape would return various phrases in response to an unknown about URI, including “Whatchew talkin' 'bout, Willis?” (a catch phrase from the TV show Diff'rent Strokes) or “Homey don't play dat!” (from a recurring skit on the TV show In Living Color).

The most commonly implemented about URIs are about:blank, which displays a blank HTML document, and simply about:, which may display information about the browser. Opera uses URIs beginning with opera for similar purposes, and many about URIs will be translated into an appropriate opera URI if entered; an exception is about:blank, which is not translated.

Note: In more recent versions of Internet Explorer, many of the following do nothing or have since been removed.