I have recently realized that I will occasionally hear notification sounds from applications that I had previously opened but no longer has any active tabs (email client, discord, etc.). I’m assuming this means they are allowed to keep some sort of connection in the background until I close all Firefox windows. Is this a bug or a “feature”? How do I turn it off? I don’t want any application running at any capacity except when I have tab(s) open for them.

Solution:

Hm, Discord didn’t have anything registered there. After some digging, I found about:debugging#workers which does list Discord stuff under “Other Workers”. It’s unsettling to see there’s no way to force confirmation and/or disable these stuff. I use Discord when I have to every once in a while. I don’t want their code running all the time in my browser…

edit: you can disable service workers with dom.serviceWorkers.enabled = false but this has no effect on Other Workers.

edit2: uBlock can disable Other Workers by setting the filter ||$csp=worker-src 'none' in My Filters and enabling Suspend network activity until all filter lists are loaded in Filter lists. It funny how this “trick” is written for Chromium-based browsers with the note that Firefox allows global disabling of service workers when the sites can just register a different type of worker with no way of disabling them. I am sure the api is less powerful than service workers bla bla bla, let me decide what runs on my browser without needing third party tools, please.