- Mobiledoc - github.com/bustle/mobiledoc-kit - framework to build editors with a standardized JSON structure
- ShareDB - github.com/share/sharedb - framework to sync any JSON document using operational transforms, add real-time collaborative editing to anything else
- Bangle.dev - github.com/bangle-io/bangle.dev - toolkit built for building editors, based on prosemirror
These use separate document structures instead of HTML, some are more modular libraries than full editors
- ProseMirror - prosemirror.net - supports collaborative editing, offers similar options to Mobiledoc for data structure
- Lexical - lexical.dev - extensible editor library from Facebook replacing Draft
- Quill - quilljs.com - modern editor built for compatibility and extensibility
- Trix - trix-editor.org - by Basecamp team used in v3
- CKEditor 5 - ckeditor.com - long history, very customizable, new architecture with built-in collaboration
- Editor.js - editorjs.io - block-based editor
- TipTap - tiptap.dev - headless, framework-agnostic, extendable editor based on ProseMirror
- Etherpad - etherpad.org - collaborative realtime editing framework, backend, and editor
- Draft - draftjs.org - rich text editor framework for React
- Slate - slatejs.org - customizable framework for building rich text editors inspired by Draft, ProseMirror, Quill
- Froala - froala.com - best editor (IMO) for traditional HTML structure
- TinyMCE - tiny.cloud/tinymce - long history, big community, completely redesigned new version 5
- Redactor X - imperavi.com/redactorx - new modern editor with powerful API capabilities
- Summernote - summernote.org - super simple editor on bootstrap
- Squire - github.com/neilj/Squire - used in FastMail webmail, better for text than images
- Trumbowyg - alex-d.github.io/Trumbowyg - html5 editor as jquery plugin
- medium-editor - github.com/yabwe/medium-editor - clone of Medium.com's editor