How do you rate something that only partially works? Great idea, but difficult to work with.

When it worked for me, it was nice to have a Firefox browser window with no UI elements at all. Like Chrome apps.

But no matter how I try, the extension doesn't seem to work except with the --app parameter added, and I only got it to work once.

I really hope the developer gets to devote more time to this, Firefox really misses this.

Just installed this, saw it didn't work at all, then tried the workaround mentioned by Firefox user 13997589. That didn't work the way I was expecting it to, and I had no idea to get out of the chromeless window. When I finally did, and finally got back to my prior tab group (via the Simple Tab Groups addon), all my history for each tab was gone (only the most recent page in each tab was preserved). I was looking for an equivalent of the Ctrl F11 feature in Vivaldi that easily TOGGLES the browser UI without going fullscreen. I'm using Firefox 85.0.2 on Manjaro Linux. I'm removing this addon for now.