CodeMirror is a versatile text editor implemented in JavaScript for the browser. It is specialized for editing code, and comes with a number of language modes and addonsthat implement more advanced editing functionality. A rich programming API and a CSS theming system are available for customizing CodeMirror to fit your application, and extending it with new functionality.

CodeMirror is an open-source project shared under an MIT license. It is the editor used in the dev tools for both Firefox and Chrome, Light Table, Adobe Brackets, Bitbucket, and many other projects.