Why can Firefox not allow permanent access to my screen?

When I join a Google Hangout and try to share my entire screen, Firefox always prompts me whether to share a window or the entire screen. I always want to share the entire screen. But when I enable the checkbox for "Remember this decision" I get this warning: Firefox can not allow permanent access to your screen.

Why does this happen? Is it because I'm on a Mac, or is it specific to macOS Catalina?

Solution 1:

I don't think it's a Mac specific problem. I saw the same message on Windows and solved it with following steps:

1. Write about:config to url searchbox and press Enter. You will see advanced Firefox settings.

2. Create variable full-screen-api.approval-required and set it to true.

3. That's it, you are now allowed to share your screen with Firefox.