How Do I Open Fixed Window in Firefox (Like Chrome App Mode)?

I was looking for something like this for a while, so here is how I made my own Firefox 'app' mode.

^{For Googlenauts with Windows/Mac 'Set Up Firefox' & 'Alternatively...' should also work on other OSs, perhaps with a few tweaks to the commands used, whilst 'Create Launcher' should work only for most Desktop Environments that implement the freedesktop 'specifactions'.}

Set Up Firefox

First run firefox --ProfileManager from terminal (you may need to close any running instances of Firefox first, or use the -new-instance option).
Create a new profile and call it app. Select the 'Default' one (IMPORTANT: otherwise by default it will start the app profile you are creating) and press 'Exit'.

Now run firefox -P app. This will start Firefox from the new app profile you just created. As removing the tabs and navigation bar is now difficult or impossible in Firefox's settings, you will need to install some extensions to remove them - these ones work, though may be better ones available that hide the bars permanently:

• Hide Tab bar with one Tab - hides the tab bar when there is only one tab open.
• Hide Navigation Bar - you need to press F2 to show/hide the nav bar

Edit: Both options of hiding the tab+nav bars is also included with Classic Theme Restorer - small icons can also be set for a more compact layout.

Now, when you run firefox -P app -new-instance (e.g. firefox -P app -new-instance ), you should get a Firefox window like this:

Also, when you open Firefox by running firefox or clicking the Firefox button, it should open your normal Firefox profile with the tab and nav bars.

Works in Firefox 30.0, 40.0, partially tested in 52.