The Firefox OS Simulator is a desktop PC tool that shows you what apps will look like on a phone that is running the Firefox OS. It is the easiest way to try out apps on Firefox OS before submitting them to the Firefox Marketplace. The Firefox OS Simulator was formerly called "r2d2b2g", but that name is too difficult.
The Simulator is packaged as a desktop Firefox add-on. You can use any recent version of Firefox, including released, Beta, Aurora, or Nightly versions.
Installing Firefox OS Simulator
Using Firefox, go to this link https://addons.mozilla.org/en-US/firefox/addon/firefox-os-simulator/
Click Add to Firefox. It's a large downlaod. Follow the prompts that appear.
Starting the Simulator
On the Tools menu, go to Web Developer and click Firefox OS Simulator. (If the menu bar is not displayed, press Alt.) The dashboard appears. screeen capture
Click the Stopped button. It changes into the Running button and Firefox OS boots up in its own window. The default size for this window is 320x480.
Note: You can also start and stop the Simulator in the Developer Toolbar command line using firefoxos start and firefoxos stop.
Navigating in the Simulator
Imitate swipe motions by clicking and dragging with the mouse.
To get back to the home screen, click the home button or press the Home key on your keyboard. What is the back key? Esc?
Mozilla is working on many WebAPIs that are intended to be available as standard in browsers. The ones currently supported in the Simulator are:
Installing an app in the Simulator
Removing an app from the Simulator
Stopping the Simulator
Updating an app
What about these
Remember that the Simulator is a brand-new tool and is still heavily under development. Please let us know if you find any bugs. link
Makes it easier to install and use ...
If you are interested in more technical details, the Simulator itself is the Firefox OS desktop client (also called the B2G desktop client), which is a build of Firefox OS that runs on Windows, Mac, and Linux. Firefox OS Simulator makes it much easier to use Firefox OS desktop because you don't have to pull code files and build it to use it. You just install the Firefox add-on and you're ready to go.
The Simulator is just a slightly-modified version of the Firefox OS desktop client with a slightly-modified version of Gaia, so the documentation for B2G Desktop, Gaia, and B2G generally will also apply to the Simulator to some extent. Here are a couple of those docs: