Magic CSS is a Chrome extension developed by webextensions.org that provides a live editor for CSS, Less, and Sass code. With this extension, users can write and preview their code in real-time, without the need to refresh the page.

The key features of Magic CSS include autocomplete, live editing of CSS files with automatic file system saving, the ability to open the code editor in an external window, CSS reloading, and the option to automatically reapply styles. The extension also offers syntax highlighting, Emmet support, a color picker, code conversion from Less/Sass to CSS, code beautification and minification, and the ability to highlight DOM elements matching CSS selectors.

Magic CSS is available for Google Chrome, Microsoft Edge, Mozilla Firefox, and Opera. It is an open-source extension, with the code available on GitHub.

Overall, Magic CSS provides a convenient and efficient way for developers to write, preview, and test their CSS, Less, and Sass code in real-time, making it a valuable tool for web development.