Having a running Firefox installed, I want to start Firefox Portable downloaded from heise. On Windows I'm running FirefoxPortable.exe -no-remote which was posted here, but always get the error: Another instance of Firefox is already running. Please close all other instances of Firefox before you try to start Firefox Portable Edition.

Things I tried:

set MOZ_NO_REMOTE=1
FirefoxPortable.exe -CreateProfile test -no-remote
FirefoxPortable.exe -ProfileManager -no-remote 

It's not a duplicate of this question since the author seems to start two instances of the same firefox installation (which also has the same default profile). In my case, I have a installed firefox instance (default profile folder %APPDATA%\Mozilla\Firefox\Profiles). The portable firefox seems to use the path Data\profile relative to FirefoxPortable.exe.

How can I start multiple Firefox instances? Is the -no-remote switch from the Firefox docs not working any more?

I'm using the latest portable version 65 of Firefox.

1 Answer

Method 1 - Flags

After testing this myself, the solution provided in this answer does indeed also work for two different installations of Firefox: Edit: According to OP, this doesn't work on their setup. The second method does, however.

firefox -no-remote -profile "profile_path"

So if you already have a running instance of your regular FF running and want to also open portable, you'd do

FirefoxPortable.exe -no-remote -profile "Data\profile"

Conversely, to open the regular install with portable already running, you'd do

firefox.exe -no-remote -profile "%APPDATA%\Mozilla\Firefox\Profiles"

_{(Actually, I only tested using absolute profiles and I already shut down my Windows PC. You might have to replace %APPDATA% with the actual path.)}

Method 2 - .ini

Another way to start multiple instances of FF portable is to add

AllowMultipleInstances=true

to the FirefoxPortable.ini in the same folder as the .exe (create it if it doesn't exist already) which, going by the documentation, automatically calls it using the -no-remote flag for you (Using this method does not guarantee the use of separate profiles though).