This is an archived page.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



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 module was removed in Firefox 36, please use the addon-httpd npm module instead.

An HTTP server for the Mozilla platform, which can be used in unit tests.


The most basic usage is:

var { startServerAsync } = require("sdk/test/httpd");
var srv = startServerAsync(port, basePath);
require("sdk/system/unload").when(function cleanup() {
  srv.stop(function() { // you should continue execution from this point.

This starts a server in background (assuming you're running this code in an application that has an event loop, such as Firefox). The server listens at http://localhost:port/ and serves files from the specified directory. You can serve static content or use SJS scripts, as described in documentation on

You can also use nsHttpServer to start the server manually:

var { nsHttpServer } = require("sdk/test/httpd");
var srv = new nsHttpServer();
// further documentation on

See HTTP server for unit tests for general information.