Edit Source extension for Firefox 13+ This extension adds an Edit Source feature to Firefox. If you right click on a document that is a known editable text document (or a link to one), you get the option to edit that content. The new built-in source-editor module is used to present the document for editing. You can find this extension on AMO at: https://addons.mozilla.org/en-US/firefox/addon/edit-source/ While editing, you can right-click in the document editor and choose the "Update Page" option, which is also available in the Edit menu and with the Ctrl-R/Cmd-R shortcut, to refresh the original document with the changes you've made in the editor. You can save your changes to your local computer using the Save option in the File menu. Neat trick: if you open the editor while viewing about:blank, you can compose fresh HTML from scratch and experiment with it!