If you are not aware, Firefox OS is Mozilla’s next innovation, an open-source Operating System that is intended to run on smartphones, tablets and TVs as well. It’s built with modern web technologies like HTML5, CSS3, etc. and runs with Linux kernel. The primary purpose of Mozilla was to bring a more open and less restricted smartphone OS to people. Code name of this project is “Boot to Gecko” or B2G.

If you are a developer and want to debug your app, or a geek kind person and want your hands on Firefox OS, you don’t necessarily need a phone running Firefox OS. Thanks to Mozilla and those dedicated developers who brought Firefox OS to desktop via Firefox OS Simulator. Excitingly it’s cross-platform as long as you have Firefox browser.

What is Firefox OS Simulator?

Firefox OS Simulator (not an Emulator) is an extension made for Firefox with which you can run real Firefox OS on your computer. It’s built with original Firefox OS components and supports most APIs. It simulates a device, Firefox OS and built-in apps. Thus you can use it test your apps, experiment or play with the OS.

Purposes of Firefox OS Simulator

1. Test Firefox OS on Desktop.
2. Playing with Firefox OS without needing of a real device.
3. Testing and debugging your apps for Firefox OS.
4. Checkout upcoming features in beta releases of the OS.

System Requirements

1. Windows, Mac or Linux (Ubuntu, etc.).
2. Firefox Browser 35 or later as of the following guide. Download link to Firefox latest version: mozilla.org/en-US/firefox/new/.
3. Firefox OS Simulator at ftp.mozilla.org/pub/mozilla.org/labs/fxos-simulator/. Note: Firefox WebIDE has option too to download and install it from Firefox’s internal UI.

The following guide is made on Firefox 36 beta in Windows 10 Technical Preview with Firefox OS 2.2 Simulator (unstable). And this guide is applicable for Mac and Linux too.

How to Install and Run Firefox OS using Firefox

1. Download and Install Firefox OS Simulator (open the .XPI file with Firefox and wait for installation confirmation message). Or you can install it later from WebIDE tool.
2. Open Firefox and press Alt from your keyboard. This will temporarily show old Menu Bar.
3. Press Shift+F8 or choose Tools > Web Developer >  WebIDE.
   
4. In WebIDE window, hit Select Runtime and select Firefox OS (use Install Simulator button if you didn’t install the simulator yet).
   
5. Firefox OS should shortly lunch in a separate window.
   
6. Slide white circle to unlock it. Here’s the home screen of Firefox OS 2.2 (unstable version):
   
7. That’s it! Use your mouse pointer to simulate touch events.

Note: You can also use old simulator add-on that simulates Firefox OS 1.1. Go Tools > Web Developer > Firefox OS to run it.

A Tour Inside Firefox OS on Desktop

• Home screen (App menu), App switcher (multi-tasker) and Notification panel:
  
• Contacts and Messaging apps:
  
• Marketplace (App store):
  
• Web Browser:
  
• Settings and Device Information screen:
  

Limitations of this Simulator

Since it’s a simulator, expect to have many limitations. This simulator has following categories of limitations: Hardware, Audio/Video codecs and Unsupported APIs. Checkout official documentation page for details and updates on limitations.

If you want to develop an app for Firefox OS, and need a kick-start guide, checkout Your first app page. For links to full documentations on Firefox OS app development, visit Firefox Marketplace Developer Hub.