My Firefox Nightly version that I have been running for some time now received an update two days ago that rendered it completely unusable. I got weird black bars on the screen that would move around on mouse movement and made it impossible to work with the browser at all. I was not too worried about that at the time as I knew that Nightly versions of the browser sometimes had hiccups like this, and that the next update would likely fix the issue again.
It did not, which left me with two options: use a different channel of Firefox in the meantime or go back to the Nightly version that worked just fine.
I decided to use Firefox Aurora in the meantime, but the second option would have worked as well. The core benefit for me was that I could simply switch to Aurora without touching the Nightly version at all. I ran it from time to time to check for updates, and the latest update today resolved the issue.
How to restore old Firefox versions
Restoring an older version of Firefox is actually not that difficult at all. There are however a couple of best practices that I'd recommend you follow before you roll back an update of the browser.
The first thing that you may want to do is back up your Firefox profile. If you can start Firefox on your system, do the following to open it:
- Type about:support in the browser's address bar and hit the enter key.
- Click on Show Folder here near the top. This opens the profile folder in the system file browser.
- Go back one directory level and copy the whole profile directory to another location on your system.
- You can alternatively use a program like MozBackup for that as well.
Downloading the old Firefox version
It is likely that you do not have the old Firefox installer on your system anymore. That's why it is necessary to download that version again from the Internet. I highly suggest you download it from the official source, that is Mozilla, and not some third party repository.
Probably the best location to download old Firefox versions is the Mozilla ftp server. Here are the links pointing to the various release channels:
- Firefox Stable and Beta and ESR: Stable versions are listed by number, while beta versions have bx added to the number with x indicating the version of that particular beta.
- Firefox Nightly and Aurora: It gets complicated here, as the directory is a mess. You may want to start with the "latest Mozilla Aurora" or "Latest Mozilla Central" directories and go from there. Most directories are listed with a date in front so that you can go back easily here.
You may need to select the right operating system first, and then the language version that you want to install. Now that you have downloaded a version that you want to try, it is necessary to install that version on your system. Note that it will overwrite the existing installation if it is of the same channel.
Blocking automatic updates
You may want to disable the automatic updating of the browser for the time being, as you may end up with the same issue after it has been updated. To block updates in Firefox, do the following:
- Tap on the Alt-key and select Tools > Options from the menu bar that opens up.
- Switch to Advanced > Update in the new window.
- Switch "Automatically install updates" to "Check for updates, but let me choose whether to install them".
Instead of installing updates to the browser automatically, Firefox will now display a prompt to you that puts you in control of the update process. You can select to install the update, or block it for the time being (for instance to wait for the next release to try again).
Words of warning
Running an older version of Firefox may put your system at risk. Mozilla patches security vulnerabilities that are found in the browser regularly, which may mean that you are running a version of the browser that is vulnerable to certain attack forms.
You may be able to mitigate some of those with proper security software. One option that you have is to use sandboxing to prevent that successful attacks reach the underlying operating system. Other options include running a mitigation software like EMET or Malwarebytes Anti-Exploit.
It is probably easier to switch the release channel if the reason for going back to an older version is a bug in the current version that you are running. This works best if you are using Nightly, Aurora or Beta versions of the browser by default, as you can go back a version at the very least in this case.
You may also want to consider switching to Extended Support Releases instead, which do not implement all the changes that regular versions of Firefox get.