i3

window manager font settings

$ cat ~/.Xresources
...
Xft.antialias: true
Xft.hinting:   true
Xft.rgba:      rgb
Xft.hintstyle: hintfull
Xft.dpi: 100

Firefox scale entire UI

about:config
layout.css.devPixelsPerPx

Chrome scale entire UI

$ chromium --force-device-scale-factor=1.5