~/.mozilla is where the main profile folder is located. ~/.cache/mozilla is where temporary data is stored like the disk cache and thumbnails you see on the new tab page and safe browsing data as you can see by the folder names. The amount of data (202MB) in this location looks normal to me when the disk cache is being used.

Did you check the folder size of each of the folders? Apart from the disk cache I only have about 50 MB in this area.

You can clear the disk cache and possibly disable the thumbnails or regularly clear this folder manually yourself. Note that current releases use the cache2 folder, so if you have the previously used cache folder then you can remove this folder.

You can create a new Boolean pref browser.pagethumbnails.capturing_disabled on the about:config page and set the value to true to disable thumbnails on the about:newtab page.

Delete the thumbnails folder in the Firefox profile folder to remove already stored thumbnails.

The amount of data (232 MB) stored in the main profile folder location looks rather high and you may want to check for files and folders that haven't been updated for over a year.

The current release uses a lot of LZ4 compressed files (.jsonlz4, .lz, .mozlz4) and you may still have older uncompressed versions hanging around unused.

You can consider to create a new profile and start afresh if you are using this profile for more than a few years.

• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles
• https://support.mozilla.org/en-US/kb/recovering+important+data+from+an+old+profile

Hi Support,

I find some backups files I erased and recovered ~43MB from ~/.mozilla.

But reading your 2nd link, my guess is it will be faster and more efficient to restart from clean profile and cache - however, this is not that simple, as my concerns are about keeping:

• FF about:config modifications
• extensions setups

so, which files shall I copy form the old to the new profile?

And BTW, I really, really, really miss the old bookmarks system - the one that was a clear tree of the whole screen height; the 5 lines today's system is surely good when you bookmark 15.42 sites, but as surely no good for more than 3,500… and this without even showing if you are in: Languages > Erlang > Frameworks > Web > Nitrogen or Physics > Supraconductors > Nitrogen or Suppliers > Gas > Nitrogen.

Modifications you made to about:config, either directly or via Options/Preferences are stored in prefs.js. You can copy this file, but it is possible that the file has obsolete prefs that are no longer supported. You can check the prefs.js file to see what settings you want to preserve and use a user.js file to initialize the new profile folder with only selected prefs you know are still supported to keep the new profile clean. The user.js file is read on every startup, so it is not a good idea to keep this file in place and best is to rename/remove user.js once it has done its job and moved over these prefs.

Data used by an extension might be stored in prefs.js if it is only a small amount of data or in a specific file or folder in case of a larger amount of data.