This is an archived page. It's not actively maintained.

Running applications


Support for extensions using XUL/XPCOM or the Add-on SDK was removed in Firefox 57, released November 2017. As there is no supported version of Firefox enabling these technologies, this page will be removed by December 2020.

Add-ons using the techniques described in this document are considered a legacy technology in Firefox. Don't use these techniques to develop new add-ons. Use WebExtensions instead. If you maintain an add-on which uses the techniques described here, consider migrating it to use WebExtensions.

Starting from Firefox 53, no new legacy add-ons will be accepted on (AMO) for desktop Firefox and Firefox for Android.

Starting from Firefox 57, only extensions developed using WebExtensions APIs will be supported on Desktop Firefox and Firefox for Android.

Even before Firefox 57, changes coming up in the Firefox platform will break many legacy extensions. These changes include multiprocess Firefox (e10s), sandboxing, and multiple content processes. Legacy extensions that are affected by these changes should migrate to use WebExtensions APIs if they can. See the "Compatibility Milestones" document for more information.

A wiki page containing resources, migration paths, office hours, and more, is available to help developers transition to the new technologies.


This page describes how to run other programs from your chrome JavaScript code, using Mozilla XPCOM interfaces. There are two ways to run programs.

Using nsIProcess

The recommended way is to use the nsIProcess interface because it is crossplatform.

Using nsILocalFile.launch()

This method is not implemented on all platforms, especially not on Unix/Linux! See nsILocalFile.launch() for details and make sure that all your target platforms support this method!

This method has the same effect as if you double-clicked the file, so for executable files—it will just run the file without any parameters.

For more information on nsIFile/nsILocalFile, see File I/O.

var file = Components.classes[";1"]