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:

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.

  • Possible duplicate of "Firefox is already running" with -no-remote
    – Entropy0
    Commented Mar 21, 2019 at 13:27
  • I don't see as a duplicate since he's starting another instance of the same firefox with the same user profile. Since I have a locally installed instance running and want to start firefox portable, the portable one is using a different profile located in Data/profile instead of %APPDATA%\Mozilla\Firefox\Profiles from installed firefox.
    – Daniel
    Commented Mar 22, 2019 at 8:23

2 Answers 2


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


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).

  • Sadly this doesn't work, I get the same error about an already running instance. -profile seems to be ignored. Even when the folder doesn't exist like FirefoxPortable.exe -no-remote -profile asdf I get the same error, no message about the non-existing profile.
    – Daniel
    Commented Mar 22, 2019 at 14:39
  • Even AllowMultipleInstances=true in Other\Source\FirefoxPortable.ini doesn't change this. No difference if using the FirefoxPortable.exe without arguments or with -no-remote -profile "Data\profile". Also tried Data/profile as path and powershell as well as cmd.
    – Daniel
    Commented Mar 22, 2019 at 14:45
  • 1
    Ok my fault, I missed the readme which inform that Other\Source\FirefoxPortable.ini is only a example. We need to copy (or create) this file to the root directory where FirefoxPortable.exe is located. Now the AllowMultipleInstances=true parameter works, which seems also more comfortable since you can start firefox using the exe file without open a command-promt first.
    – Daniel
    Commented Mar 22, 2019 at 14:49

The solution that worked for me. https://portableapps.com/comment/228523#comment-228523

  1. From the directory where your FirefoxPortable.exe is (let's call it appRootDir) you go to directoty Other\Source\
  2. Copy the file FirefoxPortable.ini to the appRootDir
  3. Change line AllowMultipleInstances=false to AllowMultipleInstances=true in the copied FirefoxPortable.ini in appRootDir

Other options like profile directory (--profile) are set in FirefoxPortable.ini.


I use FirefoxPortable of version 124.0.1

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