Online Rich-text editors, or JavaScript based HTML WYSIWYG editors, are web components that allow users to edit and enter text within a web browser. Rich-text editors are powerful web-based WYSIWYG ("what you see is what you get") editors used in numerous ways to enhance the output by applying formatting to the contents.
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In this article, we present 12 free online rich-text editors that can be easily embedded in websites.
Tiny MCE
TinyMCE is the most used WYSIWYG editor in the world, it is used by millions of people around the world for editing content. TinyMCE is an open source, lightweight and highly customizable through an intuitive API.

TinyMCE | Demo | Download
CKEditor
CKeditor is another wildly popular open source online rich-text editor with the ability to automatically detects and cleans up text that's copied from Microsoft Word documents.

CKEditor | Demo | Download
Cross-Browser Rich Text Editor (RTE)
The Cross-Browser Rich Text Editor (RTE) is based on the designMode() functionality introduced in Internet Explorer 5, and implemented in Mozilla 1.3+ using the Mozilla Rich Text Editing API.

Cross-Browser Rich Text Editor (RTE) | Demo | Download
Damn Small Rich Text Editor
Damn Small Rich Text Editor (DSRTE) is a lightweight, free rich-text editor built on top of the jQuery library and a PHP backend. It's plugin-enabled, has image-uploading capabilities, and an HTML cleanup feature to tidy up messy markup.

Damn Small Rich Text Editor | Demo | Download
NicEdit
NicEdit is a Lightweight, Cross Platform, Inline Content Editor to allow easy editing of web site content on the fly in the browser.
NicEdit Javascript integrates into any site in seconds to make any element/div editable or convert standard textareas to rich text editing.

NicEdit | Demo | Download
MarkItUp!
markItUp! is a JavaScript plugin built on the jQuery library. It allows you to turn any textarea into a markup editor. Html, Textile, Wiki Syntax, Markdown, BBcode or even your own Markup system can be easily implemented.

MarkItUp! | Demo | Download
FreeTextBox
FreeTextBox is the most-used HTML editor for ASP.NET. It is compatible with IE on the PC, and Mozilla and Firefox on all platforms.

FreeTextBox | Demo | Download
Free Rich Text Editor
Free Rich Text Editor is an extremely easy to use FREE javascript based HTML WYSIWYG editor for your website, it can easily be implemented into any existing content management system or other web application with no knowledge required in programming or javascript. Only 3 lines of code required to set up the editor. It also now outputs as XHTML compliant code!

Free Rich Text Editor | Demo | Download
openWYSIWYG
Packed with every rich text editing feature you need, openWYSIWYG gives you total control over formatting your text. The ultimate 'textarea' replacement for your content management system.

openWYSIWYG | Demo | Download
Whizzywig
Whizzywig is a free JavaScript web-based rich-text editor. Aside from features you’d expect from a rich-text editor, Whizzywig also has a Spanish and German version, a web-safe color picker to change your text’s colors, and custom-designed UI controls.

Whizzywig | Demo | Download
Web Wiz Rich Text Editor
Web Wiz Rich Text Editor (RTE) is a free WYSIWYG HTML RTE that replaces standard text areas with an advanced Word-style HTML area.
Using this tool you can change any text area on your site into an HTML area with real-time WYSIWYG formatting. Useful for many purposes from basic submission forms to advanced CMS (Customer Management Systems).

Web Wiz Rich Text Editor | Demo | Download
YUI Library Rich Text Editor
The YUI Library Rich Text Editor is a UI control that replaces a standard HTML textarea; it allows for the rich formatting of text content, including common structural treatments like lists, formatting treatments like bold and italic text, and drag-and-drop inclusion and sizing of images. The Rich Text Editor's toolbar is extensible via a plugin architecture so that advanced implementations can achieve a high degree of customization.

YUI Library Rich Text Editor | Demo | Download
If you know anything missing that can be a great addition to this list, you can suggest by using the comments box.