Firefox scrollbars - desktop PC - are, from my point of view, too thin (me, 50+ years old). I cannot exactly recall what version it was, it started to annoy me. I used an extension (Custom Scrollbars - you can find it as Firefox add-on) in the meantime, but this does not work anymore on my Ubuntu MATE 21.10 PC with Firefox 98.0.1.
Searched for a possible solution and found this topic (Tweaking your Scrollbar Settings). Unfortunately, the css based on the recommendations in the topic did change the scrollbars in some apps - e.g. Caja, Eclipse, etc. - but NOT in Firefox!
But, further searching led me to this:
- open a new tab in Firefox
- in the address bar type
about:config
- click Accept the Risk and Continue
- in the Search preference name field type
widget.non
A list of preferences starting with widget.non will be shown.
What I've changed:
widget.non-native-theme.gtk.scrollbar.thumb-size => set to 1.50
widget.non-native-theme.scrollbar.size => set to 16
widget.non-native-theme.scrollbar.size.override => set to 16
You may also want to consider following preference:
widget.non-native-theme.gtk.scrollbar.allow-buttons (I set it to true)
Hope this helps
By the way, the "Custom Scrollbars" add-on, is still in use here - it still allows customising the color of the scrollbar