Code Mirror: In-Browser Code Editing Made Easy

CodeMirror is a JavaScript library that can be used to create a relatively pleasant editor interface for code-like content – computer programs, HTML markup, and similar. If a mode has been written for the language you are editing, the code will be coloured, and the editor will optionally help you with indentation.

CodeMirror supports Autocompletion, Mode overlays, Search/replace, Code folding, HTML editor with preview, Auto-resizing editor, Setting breakpoints, Highlighting the current line, Highlighting selection matches, Theming, Stand-alone highlighting, Full-screen editing, Mode auto-changing, Visible tabs, Autoformatting of code, Emacs keybindings and Vim keybindings.

All of CodeMirror is released under a MIT-style license. To get it, you can download the latest release or the current development snapshot as zip files on GitHub.

Requirements: JavaScript Enabled
Demo: http://codemirror.net/
License: MIT License