In Firefox, is there a counterpart to Google Chromes -app option?

Solution 1:

Short answer: No.

Firefox has never had had a command-line switch like you're describing, and you're far from the first person to wish it did. In previous versions (up to FF 85), the about:config preference browser.ssb.enabled achieved this fairly well, but it was removed. (Read: Mozilla drops support for PWAs)

The closest option as far as CMD switches are concerned is --kiosk to run in Kiosk mode, which is full-screen, cannot be minimized, and disables a lot of basic functionality, including the ability to right-click. No frame is visible at all, unlike Chrome's -app switch which leaves a frame and visible title bar, among other things.

Similar questions have been posed on Superuser, where this is one possible answer (however, it involves executing some Javascript, and I could not get it to work from Firefox's browser console, although interestingly it did work from Chrome's).

Currently, this is the most commonly recommended workaround:

1. Create a new profile via about:Profiles (let's name the profile "pwa")
2. Create a userChrome.css file in that profile folder (instructions)
3. Add CSS to remove whatever toolbar items you want. Reddit's r/FirefoxCSS is a good resource for this. This gist is a good start for Chromeless CSS.
4. Create shortcuts to your "app" targeting "C:\Program Files\Mozilla Firefox\firefox.exe" -P pwa --new-instance <url> (where "-P" is the -ProfileManager argument and "pwa" is the name of your custom, chromeless profile.)

There are several downsides to this approach, including that it requires a fair amount of setup, future Firefox updates may break it, and the biggest problem for most: This new profile will not have any of the same cookies, history, bookmarks, extensions, or other settings as your primary profile, and links opened from your pwa profile will not open in your primary profile (edit: this last point may actually be possible by installing something like the Open With extension in your pwa profile, then setting it to target your Firefox main profile. It would be a slow and resource-heavy way just to open tabs, though).