One last thing: you may have noticed the big ‘Refresh Firefox…’ button in the about:support section.

Instead, close Firefox, and then go to your Firefox profile folder, and if you see anything other than a single sessionstore.js or sessionstore.jsonlz4 file – in other words if you see duplicate session restore files, delete them. So in theory, if you see any file called something starting with “sessionstore.js” or “sessionstore.jsonlz4” (depending on your version of Firefox) or any derivation thereof (such as ‘sessionstore.js-2’ for example) while Firefox is open, you should be able to delete it. Now, the thing is, Firefox only creates these session restore folders upon being closed. This will show you your Firefox profile folder in Finder (as you would expect).

To check to see if this is happening, go back to that ‘about:support’ page, and this time, again under the Application Basics section, find the line that says ‘Profile Folder’, and click on the ‘Show in Finder’ button. And sometimes Firefox creates a duplicate session restore files. Delete any duplicate Session Restore filesīy default, Firefox creates a ‘session restore’ file, in case it has to, well, restore your session. If that, along with enabling Multiprocess Windows, fixes the problem, then start re-enabling your add-ons one at a time until you figure out which one is the problem child. However if you are still experiencing a problem after doing this, try these additional steps: Disable your add-ons and re-enable them one at a timeĭisable all of your Firefox add-ons. This alone may take care of your problem with Firefox slowing down. It should be there, and it should say ‘Enabled by user’. In the ‘about:support’ section, under Application Basics, look for a listing for Multiprocess Windows. To check that this has worked, go to ‘about:support’ in Firefox. It will probably be set to ‘false’ by default select ‘true’ and then click on ‘OK’. A ‘New boolean value’ dialogue box will appear at the top of the page type:Īs soon as you click on ‘OK’, you will get the next dialogue, from which you select whether -enable should be set to ‘true’ or ‘false’.

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