FreeTextBox - FreeTextBox is the most-used free ASP.NET WYSIWYG HTML editor featured in open source and commercial projects.
Froala Editor - Froala Editor is a WYSIWYG HTML editor that enables rich text editing capabilities for the applications.
Froala Editor V2 - A beautiful modern WYSIWYG HTML text editor
CKEditor - Real-time collaborative future-ready rich text editor
Summernote - Summernote is a JavaScript library that helps users create WYSIWYG editors online.
TinyMCE - TinyMCE is a content editor that functions as a plug-in for Wordpress websites.