ckeditor
CKEditor 4 has features found in desktop word processors such as styles formatting (bold, italic, underline, bulleted and numbered lists), tables, block quoting, web resource linking, safe undo function, image inserting, paste from Word and other common HTML formatting tools. Also CKEditor 4 has built-in spell checker functionality provided as plug-ins by WebSpellChecker LLC. By default, it is available for free with a banner ad.[6] It checks the spelling of the text and marks all errors with a red wavy line and allows the user to choose one of the correct suggestions.
There are currently many plugins available with CKEditor 4 to serve different needs, e.g. CKFinder and Accessibility Checker (the CKSource’s plugins). CKFinder is a file manager for including files and images within content created with the editors. It is compatible with both CKEditor 4 and 5 and is available under commercial license.
Accessibility Checker is available under both Open Source and commercial licenses.
Real-time collaborative editing
CKEditor 5’s architecture and custom data model makes it possible to enable real-time collaborative editing.
A custom collaborative solution can be built by using the CKEditor 5 Framework components and real-time collaborative editing can be enabled by connecting to the CKEditor Cloud Services.
A ready to use, drop-in component based on CKEditor 5 (Letters) offers a complete solution for real-time collaborative writing.[12]