1. Download the latest Desktop version of Firefox from this page and save the setup file to your computer.
2. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

More information about reinstalling Firefox can be found here.

Please report back to say if this helped you!

Thank you.

If I reinstall, will I lose everything? I realize I may not have a choice, but if there is an option to prevent losing several years worth of bookmarks, that would be a good thing. Thank you.

Your personal data like bookmarks is stored in the Firefox profile folder, so you won't lose personal data when you reinstall or update Firefox, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

An error message like XPCOM missing or about platform version or entry points not found can happen because of a failed Firefox update that left you with a mixture of old and updated files in the Firefox installation folder. This can happen in case security software was keeping a handle on some of the files in the Firefox program folder preventing Firefox from replacing all the files. You need to do a clean reinstall and remove the Firefox program folder to ensure that all files are replaced. You may have to disable security software temporarily in case the problem persists.

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

No, you shouldn't lose anything. A program is separated from your data.

If you want, you can copy your profile for a backup -> https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data#w_finding-your-profile-without-opening-firefox

Thank you. I think I'm going to have to wait until my son is home tomorrow; I just don't know enough and don't want to do the wrong thing. If I screw up, I can't get it back. Son's not a computer geek, but at least knows more than I do!

Hi Sue, if you want to be sure you have a backup of your Firefox data before reinstalling/updating, the following article has the steps for making a copy of your Firefox profile folder -- a profile folder is a data folder that stores bookmarks, saved logins, history, etc.

Back up and restore information in Firefox profiles

Something went wrong with updating from 120.0 to 120.0.1 and your Firefox installation got corrupted.

Next Tuesday (Dec 19th) 121.0 will be released, so maybe wait for that new version.

Finally have enough brain power to try and tackle this myself. Tried to open my Profile. Followed instructions for Finding Profile Without Opening Profile. Typed this in the box: %APPDATA%\Mozilla\Firefix\Profiles\ and got an error message saying that the location is unavailable . . . Tried several times with same result each time.

So I can't back up my profile. Now what do I do?

Thank you in advance.

Sorry--it was " Finding Profile Without Opening Firefox."

To Moderator, wait for the new version and then what?? Mozilla crashed while trying to upload the new version Saturday night (yes, this was only 12/16, but the prompt was to upgrade Mozilla). But it doesn't matter--every time I click to open Mozilla I get the same blank page with the same error message in the middle:

Error: Platform version '120.0.1' is not compatible with minVersion>=120.0 maxVersion<=120.0

How do I open Mozilla and not get an error message? Are you saying I should go ahead with the download?

I guess I will try following TyDraniu's instructions . . .

Clearly you can all tell that absolutely nothing about computers is my forte, which is why I hesitated to do anything at first. Son has been too busy to help yet, so here I am . . . I NEED some of those bookmarks; I have been unable to locate some info I need through new searches with a different server, thus I am forced to try to get Mozilla back . . . Again, thank you all for the guidance . . . here goes . .

The reason I said to wait for 121 is because that would save you another reinstall in case it would go wrong again with updating from 120.0.1 to 121.0. Only a (clean) reinstall will help in case of a messed up Firefox installation like in your case.

Reinstall Firefox:

• https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems