May 26, 2019

How to run the Firefox Smartphone OS Simulator on Desktop and test the apps?

The Firefox OS Simulator is a piece of a add on in Firefox that simulates a Firefox OS device, and runs on the desktop. This means that in many cases, you don’t need a real device to test and debug your app. It runs in a window the same size as a Firefox OS device, includes the Firefox OS user interface and built-in apps, and simulates many of the Firefox OS device APIs.



Installing the Firefox Simulator add-on

The Simulator is packaged and distributed as a Firefox add-on. To install it:

Step 1:
Using Firefox, go to the Simulator’s page on

Step 2:
Click “Add to Firefox”.

Step 3:
Once the add-on has downloaded you will be prompted to install it: click “Install Now”.


This add-on is large (50-70MB), because it bundles a complete simulation of Firefox OS, including its default apps. So it takes multiple seconds for Firefox to install the add-on. Sometimes it takes so long that Firefox’s Unresponsive Script dialog appears. If that happens, press the Continue button to let Firefox continue installing the add-on. It will eventually succeed.

After installing it, go to Web Developer > Firefox OS Simulator to access its features. The Dashboard is the tool you use to add your app to the Simulator and run it. Here’s what it looks like:

Running the simulator

On the dashboard, On the left side you can see “Simulator Stopped”, Click on it and the simulator will start.


Add a app


To add a packaged app to the Simulator, open the Dashboard, click “Add Directory” and select the manifest file for your app.  To add a hosted app, enter a URL in the textbox where it says “URL for page or manifest.webapp”, then click “Add URL”. If the URL points to a manifest, then that manifest will be used. If it doesn’t, the Dashboard will generate a manifest for the URL: so you can add any website as an app just by entering its URL.

Note:This add-on is incompatible with Firefox 26 and greater. Please use the App Manager with the new Simulator add-ons.
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About Bhattarai Diwas (thenepaltech) 213 Articles
I'm an Engineer and have Bachelor's Degree in Electrical and information technology. Right now I am working as a software developer in Germany. All in all I love programming and I am a tech geek.