Good, but messy It works well, the add-on should be cleaned up. You should remove the unused files from the xpi file, namely: The .svn folder and nsOpenDownloadListeners.idl file from the components folder The following files from the chrome.jar/content folder: moz_overlays.*, moz_listeners.*, firefox_overlay.* and contents.rdf.in Also you should clear out the mozOpenDownload folder on browser