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.



Examples outlined in this document are no longer relevent in regards to the Twitter API calls and need to be updated

Make simple network requests. For more advanced usage, check out the net/xhr module, based on the browser's XMLHttpRequest object.




This constructor creates a request object that can be used to make network requests. The constructor takes a single parameter options which is used to set several properties on the resulting Request.


options : object
Optional options:

Name Type  
url string,url

This is the url to which the request will be made. Can either be a String or an instance of the SDK's URL.

onComplete function

This function will be called when the request has received a response (or in terms of XHR, when readyState == 4). The function is passed a Response object.

headers object

An unordered collection of name/value pairs representing headers to send with the request.

content string,object

The content to send to the server. If content is a string, it should be URL-encoded (use encodeURIComponent). If content is an object, it should be a collection of name/value pairs. Nested objects & arrays should encode safely.

For GET and HEAD requests, the query string (content) will be appended to the URL. For POST and PUT requests, it will be sent as the body of the request.

contentType string

The type of content to send to the server. This explicitly sets the Content-Type header. The default value is application/x-www-form-urlencoded.

overrideMimeType string

Use this string to override the MIME type returned by the server in the response's Content-Type header. You can use this to treat the content as a different MIME type, or to force text to be interpreted using a specific character.

For example, if you're retrieving text content which was encoded as ISO-8859-1 (Latin 1), it will be given a content type of "utf-8" and certain characters will not display correctly. To force the response to be interpreted as Latin-1, use overrideMimeType:

var Request = require("sdk/request").Request;
var quijote = Request({
  url: "",
  overrideMimeType: "text/plain; charset=latin1",
  onComplete: function (response) {

anonymous boolean If true, the request will be sent without cookies or authentication headers. This option sets the mozAnon property in the underlying XMLHttpRequest object. Defaults to false.


The Request object is used to make GETHEADPOSTPUT, or DELETE network requests. It is constructed with a URL to which the request is sent. Optionally the user may specify a collection of headers and content to send alongside the request and a callback which will be executed once the request completes.

Once a Request object has been created a GET request can be executed by calling its get() method, a POST request by calling its post() method, and so on.

When the server completes the request, the Request object emits a "complete" event. Registered event listeners are passed a Response object.

Each Request object is designed to be used once. Attempts to reuse them will throw an error.

Since the request is not being made by any particular website, requests made here are not subject to the same-domain restriction that requests made in web pages are subject to.

With the exception of response, all of a Request object's properties correspond with the options in the constructor. Each can be set by simply performing an assignment. However, keep in mind that the same validation rules that apply to options in the constructor will apply during assignment. Thus, each can throw if given an invalid value.

The example below shows how to use Request to get the most recent tweet from the @mozhacks account:

var Request = require("sdk/request").Request;
var latestTweetRequest = Request({
  url: "",
  onComplete: function (response) {
    var tweet = response.json[0];
    console.log("User: " + tweet.user.screen_name);
    console.log("Tweet: " + tweet.text);

// Be a good consumer and check for rate limiting before doing more.
  url: "",
  onComplete: function (response) {
    if (response.json.remaining_hits) {
    } else {
      console.log("You have been rate limited!");



Make a GET request.


Make a HEAD request.


Make a POST request.


Make a PUT request.


Make a DELETE request.









The Request object emits this event when the request has completed and a response has been received.


Response : Listener functions are passed the response to the request as a Response object.


The Response object contains the response to a network request issued using a Request object. It is returned by the get(), head()post()put() or delete() method of a Request object.

All members of a Response object are read-only.



The URL of the response content.


The content of the response as plain text.


The content of the response as a JavaScript object. The value will be null if the document cannot be processed by JSON.parse.


The HTTP response status code (e.g. 200).


The HTTP response status line (e.g. OK).


The HTTP response headers represented as key/value pairs.

To print all the headers you can do something like this:

for (var headerName in response.headers) {
  console.log(headerName + " : " + response.headers[headerName]);


Boolean indicating if the request was anonymous.