[mdo]

All of GitHub is basically in pixels, save for our Markdown styles—for easy modification across devices, we use `em`s. It'd be a huge project to update that to `rem`s anytime soon.

[andreash]

If you'd make it from scratch today, what technique would you use? html {font-size:62.5% } with REM?

[mdo]

Set an HTML font-size—likely 16px—and use body { font-size: 1rem; }. Allows for easy media query scaling of type.