I am on elementaryOS Hera and have an interesting phenomenon where some blackish bar occludes part of Firefox's viewport:

enter image description here

Also you can see that the viewport is cropped somehow (see the beige help box to the right). It is not part of the webpage, and opening Developer Tools leads to another black bar at the bottom:

enter image description here

The only things I did recently where enabling webrender in about:config (reverted, no change) and running sudo apt install mesa-* (since reverted, no change).

Firefox Version: 73.0.

What I've tried

Starting FF in safe mode, without plugins, removes the problem. However, disabling manually all my addons does not help, so it must be something else about safe mode that does it.

Removing prefs.js preferences also does not solve the issue.

What could be causing this? FWIW, I have an Nvidia RTX 2070 Super.

1 Answer 1


It was webrender after all. Disabling it in prefs.js and restarting FF helped. Unsure why going through about:config didn't.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.