Firstly, I wouldn't recommend going back to the old version. Older versions are not maintained by Mozilla anymore and may contain a significant number of security issues that have been discovered and fixed in newer versions.

If your system is having issues handling multiprocessing in the new Firefox, you can try unchecking the Use recommended performance settings option in the settings and setting the Content process limit option to 1. This will limit the number of processes that Firefox creates for content and can improve performance on certain systems. You'll still see multiple processes running (for Firefox, extensions, content, etc) but there will be fewer. In the end, multiprocessing does improve Firefox's performance and prevents crashing.

As for the video blockers, extensions on pre-Quantum versions of Firefox are not compatible with Firefox Quantum. However, most of the popular extensions did create a Firefox Quantum compatible version of their extension. You could try one of those.

If you would still like to go back to a previous version of Firefox and are prepared to accept the risks of doing so, it's possible to disable updates on Firefox.

I'm assuming you are trying to set the DisableAppUpdate value in your registry. That won't work because you are planning to go back to an older version of Firefox, where that value is not supported. Basically, you would install the old version of Firefox and will just update back to the new version anyway.

What you need to do is first downgrade back to the version of Firefox that you want and then either select the Never check for updates option in the Firefox settings or change the app.update.enabled preference in the Firefox about:config page to false.

Note: Some versions of Quantum change how the data files are set up, so they are not backward compatible.

I understand the security issues with the older versions. I secure my system in other ways, so this is not an issue for me. I am currently pursuing an IT degree, so I'm not computer illiterate.I have owned my current system for 9 years, and have never had an intrusion of any kind, and I check it regularly. I do not like Quantum, as it does not provide the customization options that the older version did. I turned off the automatic updates specifically because I did not want Quantum. I have enabled two autoplay blocker extensions since the update, and neither of them work. Is there any way to return my system to the version that I previously had?

I am having trouble with one other issue. I have had the same version of Firefox for about two years, and this was the first time that it updated after I changed the settings. Why did it suddenly do it now, after not updating for so long?

I understand your worries about Quantum. I am still using v54, and I have no real issues.

First, as my first post said:

Note: Some versions of Quantum change how the data
files are set up, so they are not backward compatible.

so going backward may not work directly.

One idea you could try is this. >Create a sync account with the current FF version. >Install the version that you want to use.

Note: You will need to install the program manually and place it in a folder of your choosing. Example: Firefox_v54

Note: When the installer is done, Do Not run Firefox. It will open to the current profile which may not be compatible.

>After the installer closes, now run Firefox using the -P switch and create a new profile.

>Once you are ready, log into the sync account you created. This should get your data into the profile.

Install Older Version Of Firefox {web link} Be sure to read everything here.

If you still want to downgrade, look under; I still want to downgrade. Click the Directory of other versions and languages link. Look for the directory of the version that you want. But, remember that old versions may have security issues.

You should also check out Firefox; Extended Support Release {web link} ESR Notes System Requirements

jesterr said

I have had the same version of Firefox for about two years, . . . .

Why it updated is unknown, but try this: How do you completely turn off update checks in Firefox v64? You can use a policies.json file to disable updates for all users. https://github.com/mozilla/policy-templates/blob/master/README.md or https://winaero.com/blog/disable-updates-firefox-63-above/