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.
General information about Firefox (version, copyright, license)
A blank page
Detailed information about the contents, size and location of the memory, disk and offline caches.
Detailed lists of configuration options, including many that aren’t available in the settings pages.
Details of the license.
The Firefox logo.
An enigmatic quote.
A list of plugins with their MIME type, version and state.