Works fine for me, I see the "Safe mode" dialog at FF start. Also "flatpak run org.mozilla.FirefoxNightly -ProfileManager" for instance. Maybe you have another active Firefox instance running? Do you see any error on console? On 05/16/2018 07:41 PM, Chris Murphy wrote: > > This: > [chris@f28h ~]$ flatpak run org.mozilla.FirefoxNightly --safe-mode > > Does not launch FF in safe mode. From the flatpak man page it suggests > arguments are at the end and are passed on to the app. So what am I > not grokking here?

On 17/05/18 06:48, Chris Murphy wrote: > But, if I have the usual Fedora included Firefox running, and use that > same command, I merely get a new window. Going to the menu to Help and > About indicates it's not Nightly. There's no flatpak error to indicate > it didn't or can't launch Nightly. > I would guess that that's a generic feature of FF, unrelated to Flatpak: If an instance of FF is already running, a new invocation just forwards to the existing instance. So it would be bugs/mis-features of FF that (a) invocations of Flatpak'ed FF forward to an already running non-Flatpak'ed FF instance, and (b) invocations of FF with --safe-mode (Flatpak'ed or not) silently forward to an already running non--safe-mode FF instance.