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.
From Firefox 53 onwards, no new legacy add-ons will be accepted on addons.mozilla.org (AMO).
From Firefox 57 onwards, WebExtensions will be the only supported extension type, and Firefox will not load other types.
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 WebExtensions if they can. See the "Compatibility Milestones" document for more.
A wiki page containing resources, migration paths, office hours, and more, is available to help developers transition to the new technologies.
Stable
Provides functions for communicating with an embedded WebExtension.
This API is supported from Firefox 51 onwards, and is only available if you have set the "hasEmbeddedWebExtension" key in package.json.
Globals
Functions
startup()
This function starts the embedded WebExtension.
Returns
Promise : a promise that resolves to an object with a single property browser.
The browser object contains the runtime APIs that the embedding add-on can use to exchange messages with the embedded WebExtension:
For example:
// SDK add-on
const webExtension = require("sdk/webextension");
webExtension.startup().then(api => {
const {browser} = api;
browser.runtime.onMessage.addListener(handleMessage);
});See the page on embedded WebExtensions for all the details on embedding WebExtensions in SDK add-ons.