SunEditor

Rich content editors should, ideally, produce clean, semantically meaningful documents while still being easy for users to understand. ProseMirror tries to bridge the gap between editing explicit, unambiguous content like Markdown or XML, and classical WYSIWYG editors. It does this by implementing a WYSIWYG-style editing interface for documents more constrained and structured than plain HTML. You can customize the shape and structure of the documents your editor creates, and tailor them to your application's needs. ProseMirror has built-in, ground-up, rock solid support for collaborative editing, where multiple people work on the same document in real time. Document schemas allow editing documents with a custom structure without writing your own editor from scratch. A modular architecture makes sure you only load the code you need, and can replace parts of the system as needed. A plugin system allows you to easily enable additional functionality.

Squire is an HTML5 rich text editor, which provides powerful cross-browser normalisation, whilst being supremely lightweight and flexible. It is built for the present and the future, and as such does not support truly ancient browsers. It should work fine back to around Opera 10, Firefox 3.5, Safari 4, Chrome 9 and IE8. Unlike other HTML5 rich text editors, Squire was written as a component for writing documents (emails, essays, etc.), not doing wysiwyg websites. If you are looking for support for inserting form controls or flash components or the like, you'll need to look elsewhere. However for many purposes, Squire may be just what you need, providing the power without the bloat.