Hi DLinMA2, here's what I suggest to discover those preferences:

Overview

(1) Create a new profile with default settings for research (2) Configure the settings you want (3) Use the prefs.js file in that profile as a reference for the customizations

For #1:

New Profile Testing

This takes about 3 minutes, plus the time to change settings.

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

Click the "Create a New Profile" button, then click Next. Assign a name like July2019, ignore the option to relocate the profile folder, and click the Finish button.

After creating the profile, scroll down to it and click the Launch profile in new browser button.

Firefox should open a new window that looks like a brand new, uncustomized installation. (Your existing Firefox window(s) should not be affected.) Please ignore any tabs enticing you to connect to a Sync account or to activate extensions found on your system so we can get a clean test.

When you are done with the experiment, you can close the extra window without affecting your regular Firefox profile. (July2019 will remain available for future testing.)

For #3:

You can view the prefs.js file in a text editor (don't double-click because Windows may execute it as a system script). This article has the steps to open the profile folder while you are currently in a window using "July2019": Profiles - Where Firefox stores your bookmarks, passwords and other user data.

Note: if you hide the prefs.js file (for example, rename it to prefsTEST.js while Firefox is closed), then July2019 will go back to default preferences. This might be useful to see whether your mozilla.cfg file works.

I compared two prefs.js files - one was the original and one had the settings applied. I used those settings in the MOZILLA.CFG file and the only option that was applied was the web page. I'm trying to create a standard config file to apply to multiple machines as an initial standard for any user that logs in.

You may have other options for some of the settings:

• Customize Firefox using Group Policy (Windows)
• Customize Firefox using policies.json
• Customize Firefox using AutoConfig

But more generally, there could be a problem with your file if lines are ignored. I'm not sure whether Firefox logs error messages anywhere in that case.

Configuring specific cookie settings might not be easy because checkboxes on the options page may effect several prefs.

Note that you can also deploy (Cookies) settings via a policies.json file.

• https://github.com/mozilla/policy-templates/blob/master/README.md

• https://support.mozilla.org/en-US/kb/customizing-firefox-using-policiesjson
• https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig