IndexedDB is one kind of client-side storage which is used by all major browsers. A Mozilla security review (published in 2010 apparently before it was introduced in Firefox) says: Nevertheless it makes it easier to fingerprint your browser particularly if you visit specific sites regularly which make use of it. You can disable it in about:config by setting dom.indexedDB.enabled to false - but unfortunately this breaks several sites. (For example, I've noticed that parts of the New York Times home page are not displayed.) This is probably the reason why it is still enabled in the gHacks user.js. So how can we deal with this problem? AFAIK, there are 2 solutions: 1. There is the Disable IndexedDB add-on. Unfortunately, exceptions for specific sites are not possible (so you have to manually allow IndexedDB for them). Furthermore, we don't know if it will still be available for Firefox 57+ as it isn't a webextension. 2. In your Firefox profile is a folder called storage which in turn contains the three subfolders default, permanent and temporary. The permanent folder is obviously used by some add-ons and should probably not be touched. Now the trick is to delete everything which is in the default and temporary folders (you'll find most probably entries from various websites) and make those two folders read-only. Needless to say, that dom.indexedDB.enabled should be left set to true. I've tried the second solution and haven't run into any problems on sites which make use of IndexedDB. It seems that those sites still think that IndexedDB is available although they cannot write to those folders mentioned above. You might want to try out this trick and report your findings!