Not working in 2023

Hasn't worked for years.

Has Always Worked Fine With Firefox On Windows But No Longer Works At All, Please Fix It!

Does not work in the new facebook version. Please fix!!!

Doesn't work on messenger.com

So far so good, nice work :)

Works

Good

On my Android 8.0 I can't tell the difference if it's activated or not by looking at the Firefox menu. There's a "Facebook™ Seen Blocker" but nothing is indicating the status.

does what it says

Nice

good