[Tip] How to Run Mozilla Firefox Portable Edition Side-by-Side with Regular Version

If you are trying to run and use Mozilla Firefox Portable Edition and regular installed version side-by-side and getting error message “Another instance of Firefox is already running. Please close other instances of Firefox“, this article will help you in resolving the issue and using both portable edition as well as local installed Firefox version simultaneously in your computer system.

The popular Mozilla Firefox web browser also comes in portable edition which doesn’t need installation. You can download the portable edition and use it in your computer system or store it on your removable USB drive (or pen drive) to carry it with you. Portable edition stores all your browsing data such as cache, cookies, favorites/bookmarks, history, login passwords, customized settings, etc inside a single folder. If you use Firefox Portable Edition in your computer, you can keep using it as it is even after formatting and reinstalling Windows. If you put it on your USB thumb drive, you can insert the USB drive in any computer and start using Firefox without need of any installation or customization.

You can download the portable edition of Firefox using following article:

Download Portable Version of Firefox, Chrome and Opera Web Browsers

If you try to use Firefox portable edition in your computer and you are already using a regular installed version of Firefox, Windows displays following error message:

It happens when you have opened installed Firefox program using Start Menu, Taskbar or Desktop shortcut and you also try to launch the portable edition of Firefox. When an installed version of Firefox is already running in a computer system and the user tries to launch Firefox portable edition, Firefox detects the existing process running in background and shows the error message.

By default, Mozilla doesn’t allow users to run 2 different editions or versions of Firefox side-by-side to prevent any kind of conflict or problem between user profiles and data. This is why you receive error message while trying to run portable edition and regular Firefox copy together.

But there is a workaround to fix this issue and run Firefox installed version and portable edition together side-by-side.

If you also want to use Firefox portable edition alongside the local installed copy of Firefox in your computer, following steps will help you:

1. Go to the folder which contains Firefox portable edition files. You’ll see various sub-folders inside it such as App, Data and Other.

2. Go to Other -> Source folder and look for FirefoxPortable.ini text configuration file present in the folder.

3. Copy the FirefoxPortable.ini and go to the main portable edition folder containing App, Data and Other folders and paste the INI file.

Now your main portable edition folder will contain FirefoxPortable.ini file along with FirefoxPortable.exe file.

4. Double-click on FirefoxPortable.ini file and open it in Notepad. It’ll show some preferences set to true/false. We just need to modify “AllowMultipleInstances” setting.

By default, it’s set to False which restricts or blocks users to run Firefox portable edition and regular installed version side-by-side.

Change the preference value to True. Just replace the False word with True given after the AllowMultipleInstances preference. In other words, replace AllowMultipleInstances=false line with AllowMultipleInstances=true in the INI file.

Save the file and now try to run Firefox portable edition alongside your local installed copy of Firefox and you’ll be able to use both versions side-by-side without any error message.

BONUS TIP:

You can also set DisableSplashScreen=true in FirefoxPortable.ini file to remove the Portable Edition logo or splash screen which appears whenever you launch Firefox portable edition.

Also Check:

[Tip] Create a Portable Quick Launch Toolbar for Windows Taskbar

[Tip] Create Portable Version of eM Client for USB Drives

Create Portable Version of “FeedDemon” RSS Reader for USB Drives

[Tip] Create Portable Version of Opera Browser and Opera Mail for USB Drives