Principle - Principle makes it easy to create animated and interactive user interface designs.
CKEditor - Real-time collaborative future-ready rich text editor
IxEdit - IxEdit is a JavaScript-based interaction design tool for the web.
Summernote - Summernote is a JavaScript library that helps users create WYSIWYG editors online.
Sublime Text - Sublime Text is a sophisticated text editor for code, html and prose - any kind of text file. You'll love the slick user interface and extraordinary features. Fully customizable with macros, and syntax highlighting for most major languages.
Froala Editor - Froala Editor is a WYSIWYG HTML editor that enables rich text editing capabilities for the applications.