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Latest commit 255bce9 Nov 14, 2016 @Rob--W Rob--W committed on GitHub Limit content script to owned websites only
The existing content script injects anywhere, even though the functionality is
only useful to a limited set of websites. Replaced wildcard '*' with a specific
list of domains to prevent conflicts between add-ons that are based on the same

Also removed the obsolete comment about adding domains, this is no longer

Firefox Extensions

Enable screen capturing in Firefox for both localhost/ and pages.

You have to deploy this addon on Firefox addons-store, yourselves.

Install from Firefox Addons Store

Check if screen capturing is enabled for your domains:

// ask addon to check if screen capturing enabled for specific domains
    checkIfScreenCapturingEnabled: true
}, "*");

// watch addon's response
// addon will return "isScreenCapturingEnabled=true|false"
window.addEventListener("message", function(event) {
    if (event.source !== window) return;

    var addonMessage =;

    if(!addonMessage || typeof addonMessage.isScreenCapturingEnabled === 'undefined') return;

    if(addonMessage.isScreenCapturingEnabled === true) {
        alert(JSON.stringify( + '\n are enabled for screen capturing.');
    else {
        alert(JSON.stringify( + '\n are NOT enabled for screen capturing.');
}, false);


Your requests to addon: checkIfScreenCapturingEnabled: ask addon to check if screen is already enabled for specific domains.

Addon responses:

  1. isScreenCapturingEnabled - Here true means domain is already enabled for specific domains.
  2. domains - list of same domains that are enabled for screen capturing.

Simplest Demo

Try this demo after installing above addon:

Wanna Deploy it Yourself?

  1. Open index.js
  2. Go to line 7
  3. Replace arrayOfMyOwnDomains array with your own list of domains
// replace your own domains with below array
var arrayOfMyOwnDomains = ['', '', 'localhost', ''];

How to Deploy?

1) Signup here:

2) Use unique-addon-name here:

3) Add your own domains here:

4) Make XPI of the directory.

[sudo] npm install jpm --global

jpm run -b nightly      # test in Firefox Nightly without making the XPI

jpm xpi                 # it will create xpi file

5) Submit the XPI here:

Follow all steps. Read them carefully. This is hard/tough step to follow. Select valid browsers. E.g. Firefox 38 to Firefox 45. And submit your addon for "review".

It will take 2-3 hours for a Mozilla AMO reviewer to review your addon. Then it will be available to public.


Firefox-Extensions are released under MIT licence . Copyright (c) Muaz Khan.