Maybe switch to the Firefox portable version.

• https://portableapps.com/apps/internet/firefox_portable

If you have a regular hard drive then you can move the profile folder to this drive or only move the disk cache.

• https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles

See also:

• /questions/1317032 How to locate and change Firefox Cache storage location

Make sure to specify a new empty folder that is only used for the disk cache.

• about:config => browser.cache.disk.parent_directory

Note that you can use a user.js file in the Firefox profile folder to ensure that the pref is always set correctly each time you start Firefox.

The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.

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

• Help -> More 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

hmm.. that is not what I asked.. I just want to know why when I update Firefox it keeps switching false to true for that disk caching setting.. I don't want to using a portable Firefox install or switch the profile directory.. ssl caching settings keeps off thankfully..

startup of Firefox is by itself not switching it. I will try the user.js method but it really doesn't answer my quest... if you don't know that is fine too. it could be a bug or intentional.

You shouldn't lose settings when Firefox updates. Possible causes are security software that keeps an handle on files in the Firefox profile folder, in this case on prefs.js. You can check if you have numbered prefs-##.js files in the Firefox profile folder.

• https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save

true, it shouldn't be doing it but it does... for me at least. prefs.js today's date 69KB prefs-1.js 01/22/2019 45KB prefs-2.js 09/11/2019 44KB there are three preference files in my profile.

You can delete the two numbered prefs.js files (prefs-1.js and prefs-2.js) from 2019. Do you have more such numbered files in the Firefox profile folder?

ok I will delete those two old files. no just those 2.

Be careful with deleting other files just because of their last modified date as some might still be used (I have a key4.db file with a 2022 timestamp used along with logins.json for the logins).

of course, I will be careful.  ;-) but I also make secure backups.. lol. key3.db key4.db both 2018

cert8.db 2018 cert9.db 2023

key3,db and cert8.db are old files and are no longer, they have bee replaced by SQLite database key4.db (encryption key for logins.json; SQLite) and cert9.db for certificate data.

"key3,db and cert8.db are old files and are no longer, " so I can get rid of them?

Yes, you can remove key3.db and cert8.db,

ok ty for the reply.