Yes, it uses contentEditable. There's a write-up from last year at http://marijnhaverbeke.nl/blog/prosemirror.html http://marijnhaverbeke.nl/blog/prosemirror.ht

Yes, it uses contentEditable. There's a write-up from last year at http://marijnhaverbeke.nl/blog/prosemirror.html http://marijnhaverbeke.nl/blog/prosemirror.html . Some details have changed (we make more use of DOM diffing and mutation observers than initially hoped), but most of the info there still applies.