CKEditor is the more common of the two in our index: it runs on 81 websites against 57 for TinyMCE, and 3 sites use both. Counts come from real scans, not vendor claims.
CKEditor is a WYSIWYG rich text editor which enables writing content directly inside of web pages or online applications. Its core code is written in JavaScript and it is developed by CKSource. CKEditor is available under open-source and commercial licenses.
TinyMCE is an online rich-text editor released as open-source software. TinyMCE is designed to integrate with JavaScript libraries, Vue.js, and AngularJS as well as content management systems such as Joomla!, and WordPress.
3 sites run both CKEditor and TinyMCE. That is 5% of the sites using TinyMCE, the smaller of the two.
Want to know which one a particular site uses? Look it up and see its whole stack, or compare two sites side by side.