Back up and restore information in Firefox profiles.{web link} I use an add-on that makes backups of my user profile, Just In Case. Unfortunately, it is not compatible with the current Firefox.

Every now and then, open the profile folder and create a copy of the current profile as is to another location on your hard drive. This way you will have a backup.

If you do this each day, you will not lose much data. This should be done with Firefox Closed.

Note: In case you need to restore from these backups, you may need to overwrite old or corrupted files.

Good advice, FredMcd.

I backup my Profiles weekly and I keep an eye on the Release Calendar.

TMG said

... When an upgrade is available and I try it, I always(?) get a message saying that the Firefox Upgrade failed and that I should download and install the latest copy. Can you guess why I now know to avoid that suggestion? ...

Download and installation of a new version of Firefox shouldn't affect the user Profile at all; same for the automatic updates. A user shouldn't need to backup their Firefox Profile on a regular basis. Regarding Fred's advice; my advice is to take it 'with a grain of salt'. He brags repeatedly about using an old, legacy version of Firefox rather than using a Quantum version. I wonder how much experience he has had with the Quantum versions? Or is he providing advice as a by-stander? And his mention of MozBackup is reeeeal dated; that extension died like 6 or 8 years ago as far as being compatible with a current version of Firefox. IMO, living in the past rather than dealing with the present state of Firefox. Don't get me wrong though, doing a backup of your Firefox Profile won't hurt you, but it's no magic elixir either.

One thing that is causing minor problems for some users is changes made with a major Firefox update that can affect userChrome.css customizations, which seems to be a "constant" for the last 4 or 5 Firefox versions. The user interface is being slowly changed, (moving from XUL to HTML a step at a time) major version by major version, which may require the user to search out how to fix what got broken.

IMO, the biggest problem with userChrome.css changes seems to affect users who insist upon using userChrome code for moving the tab-strip to the top of the browser. And many of the codes that are being used are over complicated and thus more vulnerable to getting broken more frequently.

That said, your thread over here - https://support.mozilla.org/en-US/questions/1264110 - from 7 months ago mentions the Beta build. That is a slightly different situation than when using a Release versions, whereas the Beta receives many more updates that the Release versions receive; along the lines of 12 to 16 (or so) updates over the 6 week Beta cycle [which is now reduced to 4 weeks].

IMO, if you aren't testing the Beta version to help with the development of Firefox and reporting the faults that you find with the "next upcoming Release version" - DON'T user the Beta version and thus increasing your frustrations with Firefox unnecessarily. I has been hard enough dealing with a Release updates every 6 weeks (not counting the "chem spill" minor version updates between the major versions), but with the new 4 week Release schedule in 2020 it will be worse with "stuff getting broken" for users who use userChrome customizations.

I understand what beta builds are supposed to be for, but they do get used for a few different reasons that are useful to many. I like to see what is coming up in the rext release just in case it seems like I might want to do a full backup (none of this "profile" crap since (A) I do not know what is and is not restored exactly as before when one restores one's FF profile after an FF "upgrade" has been installed; and (B) FF does not lend itself to installing new releases that are completely isolated from existing installations, at least not without a lot of hassle.

 Storage space is dirt cheap.  When I am developing software, I usually have at least one full backup of every version that lasted through a full workday of testing -- even if whatever change being tested was essentially a false path I had no intention of following even if it functioned just as I wanted it to.

 I think the main problem I have with the way new releases of FF often if not always (as my experiences suggest) overwrite the the currently installed release is that they wipe out addons, drop many of the current settings, and DO NOT EVEN ASK the user if a COMPLETE BACKUP of the current installation should be made before it is upgraded, overwritten, or wiped and replaced.

 When current prices for Samsung 1.0 TB SSD storage devices start around $100 (it has sometimes been less expensive to buy the external version of an SSD and keep just the drive itself for internal installation in recent years) there really ought to be a settings option that lets the user  set an option to "Automatically make full backup of FF N(current) before upgrading to FF-N+1(new)" ... and yes, check to make sure there is at least 5% (or some reasonable arbitrary amount) of the storage device free.

Regards, TMG

That "profile crap" is where user data is saved for Firefox; a completely separate directory from the Firefox program files.

As far as installing Firefox, the new installation will use an existing Profile. But since Firefox 67 if the new installation versions differs from the previous (or current version), Firefox may create an additional, new Profile for the new installation to use.

Type about:profiles in the URL bar and hit Enter. You can see how many Profiles there are for Firefox.