Cache Status is a Firefox add-on that can clear the RAM and Disk Cache of Firefox automatically when it reaches a defined number. The add-on is not yet compatible with Firefox 3 right away but it works flawlessly if the install.rdf file is alterered that comes with the installation package.

To do that you need to download the Firefox extension from this link by right-clicking on the button and saving it to your hard disk. Now open the downloaded file with an unpacker like Winzip, Winrar or 7-Zip and extract the install.rdf file from the package.

Open install.rdf in a text editor and search for the line that begins with . Replace the complete line with the following line 3.0 and save the file. Now add the file to the installation package again and double-click it after that to start the installation.

The add-on will display the RAM usage of Firefox 3 in the status bar and it is possible to clear the RAM manually by right-clicking those information. If you want the RAM and Disk cache to be automatically cleaned you need to open the options of the add-on under Tools > Add-ons and click on the Options button of that add-on.

Just check the automatically clear .. options and define a percentage for each value when the automatically cleaning should kick in.