Are you bookmarks and settings erased when you restart Firefox?

It sounds like maybe you are launching Firefox from the *****.dmg file instead of locally on your computer. Doing so causes this type of issue because every time you open Firefox it's detected as a new installation and a new blank profile is created.

You can verify this is the case by going to the about:profiles page in Firefox. That page will probably contain a ton of profiles; one for each time you opened Firefox.

You need to copy the firefox.app file from the *****.dmg into the Applications folder on your computer.

See How to download and install Firefox on Mac for more information.

Hope this helps.

Hi Branton, thanks for your speedy response.

There are no additional profiles in the profiles page, only the default one Firefox has upon startup and the ones I've created so far.

My bookmarks are not erased when I start Firefox, however after logging into the user, it didn't remember my preferences, e.g. I added the 'show your bookmarks' star icon to the top right so I could easily access my bookmarks, and this was not there, I had to add it again.

You are asked to log into Firefox Sync each time you start Firefox? If you skip logging into Firefox Sync are your bookmarks still there?

Firefox Sync means the user profiles, right? In answer to your question, it doesn't ask me to log into the profile each time I start Firefox, but when I saw none of my tabs had opened, I checked under the top right menu and could see I wasn't logged into the profile, so I logged in.

Interestingly, I just tried logging into another profile, and the tabs DID sync. Does this mean it's something to do with a setting somewhere? Both these profiles have the setting ticked for "restore previous session".

Ok, so I just logged out of that profile, quit Firefox, then reopened. It was still logged OUT of the user, yet all of my bookmarks are there, and it even restored the previous session's tabs too.