I know about:Tabs
goes to the New Tab page, and about:blank
goes to a predictably blank page.
But how and why did this function come about? And are there other keywords that come after about:
with different functions?
The about:
is a URI scheme. As explained here on the Wikipedia page on the 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 standardized.
So this is basically an internal web browser URI that is reserved for doing specific things within a web browser. What things? As the official IANA (Internet Assigned Numbers Authority) web site, on a basic level it’s stuff like this:
about:blank
URI references a blank page.about:invalid
URI references a non-existent document with a generic error condition. It can be used when a URI is necessary, but the default value shouldn't be resolveable as any type of document.about:html-kind
URI identifies the vocabulary of kind values in HTML specifications from W3C and WhatWG.That said, what I listed above are just the bare basics: Look at the Wikipedia article again to find browser specific about:
URI schemes.