[MalcolmDwyer]

But watch out for 100vh on mobile. It doesn't account for the sometimes there, sometimes not there address bar.

To solve that, there's svh (small), lvh (large), and dvh (dynamic).

If you want to make a div stretch to the height of the window, so that something can appear exactly at the bottom before scrolling,

{ height: 100vh; height: 100svh; }

works best... the first line is there as a fallback for the few browsers that don't yet support svh... and if svh is supported it will replace the first line.