Data is synced from the Chrome Web Store. View the official store page for the most current information.
From the context menu (right click), you can "View source" "View selection" or "Edit text" with your favorite editor. Enabled in (X)HTML, JavaScript, CSS, MathML, SVG, XML, etc.
To use withExEditor, you also need to prepare a host which executes your editor. Please download the host for withExEditor from asamuzaK/withExEditorHost https://github.com/asamuzaK/withExEditorHost.