The default line height is defined by the font (and the browser may influence it in other ways too?), but it’s distinct from the em. (It’s easy to try in a brow

The default line height is defined by the font (and the browser may influence it in other ways too?), but it’s distinct from the em. (It’s easy to try in a browser. I see values like 18.78px and 19.33px and 21.67px on my 16px text.)