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How to run multiple instances of Firefox at the same time
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How to run multiple instances of Firefox at the same time

by AshwinJanuary 29, 2016

Mozilla Firefox is a fantastic browser, not counting the recent controversial changes of course.

run multiple instances of Firefox
But the fact that it is open source, and customizable is an admirable fact.

Due to this, the browser has been forked into various different applications, based on Firefox’s source code. WaterFox, Palemoon and Comodo IceDragon are a few of the popular ones. But, have you ever tried two different  Mozilla Firefox browsers running simultaneously?

If you have, you would have noticed a pop-up message which says “Mozilla Firefox is already running. Please close the older browser”.

And if you tried opening two instances of the same version of Firefox, it will just open two different Windows. Is it actually possible to have two different instances running simultaneously? Absolutely, you can, and it is not limited to two, you can have as many as you’d want to.

First of all, there is something which you should understand about how Firefox stores your add-ons, settings etc. It is stored in your Firefox Profile, which is a local file stored on your PC.

This is the reason why you cannot run multiple instances of Firefox by default. Because the settings and the other info have to be saved to a profile, and by default there is only one. So, the first thing to do is to create a new Firefox Profile.

How to create a new Firefox Profile:

1. Save your work, and close Firefox if you have it open.
2. Press the key combo Windows + R.
3. Copy and paste the following code into the the Run command window and press enter.

firefox.exe -P

multiple Firefox profiles Firefox profile manager 2

4. This will open the Firefox Profile manager.
5. You will see a “Default” profile, with some numbers next to it. (I renamed mine a longtime ago, so it doesn’t show Default in the screenshot)

Firefox profile manager
6. Click on the Create Profile button, and assign a new name to it. For example: Firefox 1

create Firefox profile

7. Disable the option which says “Use the selected profile without asking at startup”.

multiple Firefox profiles

Now you have two profiles in Firefox.

How to run multiple instances of Firefox at the same time

1. Now, you have to run a specific profile. For that you can use the following command.

“C:\Program Files\Mozilla Firefox\firefox.exe” -P “Profile name” -no-remote

2. Instead of “Profile name”, use the actual name you assigned to the profile, for instance “Firefox 1”.

3. Similarly, run the command again with the other profile name instead.

And you should have two instances of Firefox running at the same time.

Why are multiple instances of Firefox useful?

For the average user, it may not be of use at all. But for people who use it for work, or work-related browsing, it is a real boon. You can have different sets of add-ons running on each profile, which is an incredible advantage.

And it also works for multiple Firefox based browsers, as you can see from the 1st screenshot, I’m running both Firefox and Waterfox together.

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