<snip> - tried same computer, user account of local admin: Firefox starts without error message - tried same computer, user account of another standard user, copy of Firefox profile folder pasted to appropriate folder: Firefox starts without error message with almost all data and settings. Missing: different GUI theme and all Addons icons in the toolbar <snip>

On the basis of those two paragraphs it seems to me that there is some problem with your user account. In the case of the other standard user, the GUI theme may need to be enabled and add-ons may need to be enabled for private windows.

Macsico said

<snip> - tried same computer, user account of local admin: Firefox starts without error message - tried same computer, user account of another standard user, copy of Firefox profile folder pasted to appropriate folder: Firefox starts without error message with almost all data and settings. Missing: different GUI theme and all Addons icons in the toolbar <snip>

On the basis of those two paragraphs it seems to me that there is some problem with your user account. In the case of the other standard user, the GUI theme may need to be enabled and add-ons may need to be enabled for private windows.

Thanks for your suggestion. Wanted to test this in the other standard user. To my surprise it wasn't necessary to perform any of the above mentioned steps as Firefox behaved like a good citizen and used my selected GUI theme. Also all add-ons icons were exactly in the expected position.

At least this showed me that there is no bad file included in the profile folder copied from my main user account.

In the meantime, the update for FF 78.9.0esr arrived and was installed. I had little hope that this might fix my problem, but this did not happen.

Yes, it is truly related to my user account. Question is, what kind of problem can stop Firefox from using a file path? On a Mac there is no centralized Registry and all settings are stored in single files. With the help of uninstaller app "AppCleaner" all related files were deleted after my first unsuccessful re-installation, but problem was the same.

I can fiddle around with folder permissions if necessary, but where to start?

Your question really relates to the MacOS so should be directed to some MacOS support. I am not a Mac user. I have a Linux OS and, if checking permissions, would look at the folder which contains Firefox settings including profile folders, then at the directory which contains all such user files and folders. I would possibly run commands to ensure that ownership AND permissions were correct.

It is likely that the current profiles.ini file isn't pointing to an existing profile.

• https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

Best is to use the Profile Manager to create a new profile and transfer some personal data from your old backup although not everything might work if this profile is really old.

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. Note that you should be cautious with copying SQLite database files if you previously had problems.

• 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)

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

Your question really relates to the MacOS so should be directed to some MacOS support. I am not a Mac user. I have a Linux OS and, if checking permissions, would look at the folder which contains Firefox settings including profile folders, then at the directory which contains all such user files and folders. I would possibly run commands to ensure that ownership AND permissions were correct.

Thank you again for your suggestion. I ran the old (old in the eyes of Apple: article was removed from their knowledge base due to some OS changes) procedure of repairing permissions for the whole home folder of the main user. No change in FF behaviour, still same error message.

To make it even more weird, I ran a test in a) the affected standard user account, b) in the local admin account and c) in the non affected standard user account by renaming the current surrounding folder containing the INI files and the profile folder.

Then Firefox war launched again and showed different results: a) in the affected user account, the error persisted and NO profile folder is created inside the surrounding folder, no "profiles.ini" and no "installs.ini". See screenshot with green selection attached.

b) and c) in the local admin user and the other standard user, a complete new folder is created with all default files and folders. See screenshot with blue selection attached.

It is likely that the current profiles.ini file isn't pointing to an existing profile.

• https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

<snip>

Thanks for pointing into this direction, but this does not solve the problem. The full folder content is working fine when using it in another standard user account.

The built-in profile manager cannot be launched as only the error message appears again. By using the extra ProfileManager App downloaded from the Mozilla homepage a new profile can be created, but when trying to use it, FF again claims that the is no profile.

Please see also my other answer as well. FF does not even create a new PROFILES.INI or a new profile folder when the old folder has been renamed or removed. When I try to use the external ProfileManager App it cannot be used and shows an error message.

Any other ideas are appreciated.

Did you check the read/write permission and the owner of Firefox folder and possible sub folders to be sure that there are no problems ?

You can try to do some maintenance.

• https://appletoolbox.com/2016/07/fix-corrupt-user-accounts-macos/

Firefox uses two locations for the Firefox profile folder. One location for your personal data (e.g. bookmarks) and another location for temporary files like the disk cache.

Location used for the main profile that keeps your personal data (Root Directory on about:profiles).

• ~/Library/Application Support/Firefox/Profiles/<profile>

Location used for the disk cache and other temporary files (Local Directory on about:profiles).

• ~/Library/Caches/Firefox/Profiles/<profile>

Did you check the read/write permission and the owner of Firefox folder and possible sub folders to be sure that there are no problems ? You can try to do some maintenance.

• https://appletoolbox.com/2016/07/fix-corrupt-user-accounts-macos/

---

Firefox uses two locations for the Firefox profile folder. One location for your personal data (e.g. bookmarks) and another location for temporary files like the disk cache.

Location used for the main profile that keeps your personal data (Root Directory on about:profiles).

• ~/Library/Application Support/Firefox/Profiles/<profile>

Location used for the disk cache and other temporary files (Local Directory on about:profiles).

• ~/Library/Caches/Firefox/Profiles/<profile>

Read/write permissions have already been dealt with for the whole home folder. It is the same procedure as outlined in the linked page. But no change in FF behaviour happened.

The page URL has been changed and is now located at (your link shows a 404): https://appletoolbox.com/fix-corrupt-user-accounts-macos/

Checked both profile folder locations in the affected account: 1) ~/Library/Application Support/Firefox/Profiles/ => this folder is present

2) ~/Library/Caches/Firefox/Profiles => this folder is not present. Maybe it was deleted during the first FF delete and re-installation actions, but I cannot remember.

At least there is nothing left with the name "Firefox" when starting FF.

My next attempt will take a little longer: - switched to non affected standard user - started FF with the profile folder copied from affected account (BTW: works like a charm) - started Activity Monitor app and opened process info - in process info the list of open files and ports was shown, copied and transferred in a LibreOffice Calc file - list was sorted alphabetically - all open files from user account folder will be inspected (this is the time consuming part)

First finding: - a folder with SavedState related to Firefox was found in the list and deleted in the affected user => not resolved

The search continues.

Success: Firefox 78.9.0esr is up and running again. This posting is written in Firefox and not in Brave Browser like my other postings before. As this is one the most weird problems in my whole computer life I like to share it with all.

The whole story written down for others maybe falling into the same trap:

Yesterday evening a massive system crash took place. After this event, the MacBook was unable to finish boot process both from internal and two different external bootable drives via USB. Completely stuck after progress indicator became slow after 80% and way later got frozen at 100%.

Then several tests were performed:

• boot system from USB memory stick with Linux (Rasperry Pi Desktop) => worked, so motherboard and (non-soldered) RAM modules seemed unaffected

• boot system with key D pressed => worked, Apple System Diagnostics reported only minor problems with non Apple RAM modules. Exchanged this RAM modules with original Apple RAM modules and got no error message. But after 7 years I am confident enough with the non Apple modules.

• removed Samsung EVO SSD from MacBook by opening case and disconnect it from SATA bus, then the old Seagate FireCuda HDD drive (it's fully loaded predecessor) was connected to SATA and booted => worked, so SSD was isolated as potential troublemaker but with unknown error. Hardware error or file system structure?

• booted from external USB volume => worked, so SSD is definitely the troublemaker

• tried to reformat SSD drive in external USB enclosure when booted from other MacOS drives => no success, as drive was completely out of reach for MacOS Disk Utility

• booted again Linux from the USB memory stick and used GParted to erase all partitions on SSD

• re-connected SSD to SATA in MacBook, re-installed MacOS via Internet Restore, restored user accounts from TimeMachine backup => worked, and Firefox just opened as Startup Item like always. YEAH!

Long story short: you should always have at least two full system backups at hand - and one bootable Linux USB memory stick, just in case the MacOS disk is too corrupted.

Being a longtime Mac user (and Ex AppleCare Advisor for 2 years) a massive file system corruption like this never happend to me and was therefore not on my list of possible suspects.

Thanks to all who tried to figure out what happened to my Profiles folder which in fact only was a visible victim of the file system corruption.