The “about:” URI schema has been around since the days of Netscape, but there is more to it than the common “about:blank” reference for an empty page. Some of these options give you an advanced view over Firefox and its cache – and others a just a bit of entertainment.

Here is a list of some common examples, all of these work in Firefox (tested in Firefox 3.6.3).

To use any of these, simply type them into the address bar.

about:

General information about Firefox (version, copyright, license)

about:blank

A blank page

about:cache

Detailed information about the contents, size and location of the memory, disk and offline caches.

about:config

Detailed lists of configuration options, including many that aren’t available in the settings pages.

about:license

Details of the license.

about:logo

The Firefox logo.

about:mozilla

An enigmatic quote.

about:plugins

A list of plugins with their MIME type, version and state.