Can't open Firefox because a copy of Firefox is already open
I use a MacBook Pro running OS Monterey and I've gotten the dreaded "Firefox is already open" message. Firefox isn't my primary browser but I do have tabs and bookmarks saved there. This has happened before, and last time I ended up following advice to delete my profile which wiped out my entire account (it was the only profile there, and I should have looked for an alternate solution because that clearly wasn't it).
I was very interested in switching from Chrome to Firefox permanently, but I'll be honest, I'm pretty frustrated that this keeps happening and putting my tabs/bookmarks/history/etc in jeopardy. If someone could provide a straightforward explanation as to how to fix this I would greatly appreciate it.
Btw, I already tried viewing FireFox in the activity monitor as I saw another site suggest and it wouldn't let me quit it (I saw it greyed out).
There's a support article. You may have to remove a lock file although the lock file on my system (not Mac) does not seem to prevent me from starting Firefox.
Thank you for responding! I don't think I saw that article when I was Googling solutions.
When I checked my Firefox profiles, I saw there were two (see attachment). I'm the only user on this computer. Does one of these need to be deleted? By the way, neither folder had a file with a .parentlock file.
Note that .parentlock is a hidden file on Mac.
I was able to install follow another support article and install OnyX, which allowed me to locate and delete the hidden .parentlock files on my profiles. I was able to open FireFox again, but for some reason this completely wiped my FireFox account and made it a default profile again. I lost everything I had stored there. I was able to get the extensions I had back from the other profile by copying them over, but my bookmarks, history, tabs, etc are all gone (even though I copied all the files from the other profile over).
Very fortunately I didn't really lose anything important because FireFox is not my default browser, but I'm still pretty frustrated by this.
You can copy certain files with Firefox closed to the current profile folder to transfer or recover personal data. Note that best is to avoid copying a full profile folder.
- bookmarks and history: places.sqlite
- favicons: favicons.sqlite
- bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
- cookies.sqlite for the Cookies
- formhistory.sqlite for saved autocomplete Form Data
- logins.json (encrypted logins;32+) and key4.db (decryption key;58+) for Passwords saved in the Password Manager
key3.db support ended in 73+; to use key3.db in 58-72, make sure to remove key4.db
- cert9.db (58+) for (intermediate) certificates stored in the Certificate Manager
- persdict.dat for words added to the spell checker dictionary
- permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
- sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)