We have already learned how to change the location of the temporary files folder of Firefox. This time we will see how to configure the size of the cache to our liking. A larger cache implies that a larger amount of offline data can be stored, which will help Firefox to load certain webpages more rapidly!
NB:If your PC is equipped with a SSD, it is not advisable to increase this value!
The default value of Firefox's cache is 50 MB.
The minimum value is 0.
The maximum value is 1024 MB.
Change the size of the cache:
Click on the Menu button > Options.
Click the "Advanced" > "Network" tab.
Tick the Override automatic cache management checkbox.
Edit the value for Limit cache to  MB of space (between 50Mb and a maximum of 1024MB).
Click on Ok to validate and restart Firefox.
Type about:config in the address bar and press Enter.
Firefox will display a security warning, click on I'll be careful, I promise!
Search for the browser.cache.disk.capacity preference, which determines the maximum cache size.
Double-click to edit (Integer value)
Increment the value to your convenience (default value 50000, which represent 50 MB)