If you are using high resolution display, scaling on Linux can be a difficult topic. Here are some hints how to get your browser user interface right.
Depending on your Window Manager (if you have one), there also can be some wm related settings. Gnome 3 for example supports scaling different.
First thing you should set (and probably already have) is adjusting the dpi setting. Get the current value with xdpyinfo | grep dots
and increase it with xrandr --dpi 300
.
The downside is that many programs (like Firefox) and window manager ignore the dpi setting.
Another option is using ui scaling, also with xrandr:
xrandr --output XXX --scale 1.25x1.25
Downside is that fonts can get blurry that way, so i prefer not to use it.
UI Scaling in Firefox is mostly isolated from operating system. Thankful there is an easy way to adjust it just in browser. Navigate to about:config, click on “I’ll be carefull i promise” and search for:
layout.css.devPixelsPerPx
Just adjust the value to your desired value, you can use decimal values like 1.3. There is also a browser addon for automatically adjusting.
Normally chromium supports HiDPI out of the box, but on some screens this is not working perfectly. You can either then start Chrome with the command line parameter --force-device-scale-factor=1.5
or check about:flags for adjusting the scaling
Opera detects your dpi setting and adjusts to it, you can also use --alt-high-dpi-setting
to adjust it to your needs.