From CSS-Tricks: https://css-tricks.com/the-current-state-of-styling-scrollbars/
If you need to style your scrollbars right now, one option is to use a collection of
::webkit prefixed CSS properties.
Sadly, that doesn’t help out much for Firefox or Edge, or the ecosystem of browsers around those.
But if that’s good enough for what you need, you can get rather classy with it:
There is good news on this front! The standards bodies that be have moved toward a standardizing methods to style scrollbars, starting with the gutter (or width) of them. The main property will be
scrollbar-gutter and Geoff has written it up here. Hopefully Autoprefixer will help us as the spec is finalized and browsers start to implement it so we can start writing the standardized version and get any prefixed versions from that.
But what if we need cross-browser support?
Here’s another one called simple-scrollbar:
I’ll embed a copy here: