Software developer, author, and host of Full Stack Radio. November 30, 2017 Update: It looks like the bug in Safari has been fixed in Safari 15, so I wholeheartedly recommend using em for media queries now. Keeping the post up for historical reasons, but the conclusion is no longer valid. In March 2016, Zell Liew published a really great in-depth post titled "PX, EM, or REM Media Queries?", where