Everybody loves pretty code, and in fact CodePen has had the "tidy" functionality since the beginning. In the Pen editor, it's in the dropdown within your HTML/CSS/JS panels. And in the Project Editor, it's in the main bar, at the top of your file editor.
So, why are we here?
You know what, this video explains it better than I ever will!
This library was brought to our attention by a few people on Twitter, so as ever, let us know if there's something you feel missing from CodePen, and we will at the least, give it a little look.