Multiple Firefox Instances

It can often be useful to have multiple Firefox browsers open at the same time. Particularly for testing web sites or any sort of web development. Or even just so you can be logged into two sites at the same time with different accounts.

Firefox provides such a feature with the -no-remote switch. The first step is to create multiple Firefox profiles. To do this, launch Firefox with the -ProfileManager switch.

On Windows click Start > Run then:
"C:\Program Files\Mozilla Firefox\firefox.exe" -no-remote -ProfileManager

On *nix launch the command:
firefox -ProfileManager

Then create a new profile. If you want to make a copy of your existing profile, simply create the new profile, then copy the current profile directory to the new profile directory.

Now you’re ready to launch Firefox with the -no-remote switch. The trick is that you need to select your second profile when you launch your second instance. So start Firefox as normal, then launch a second browser.

On Windows click Start > Run then:
"C:\Program Files\Mozilla Firefox\firefox.exe" -no-remote -P "secondprofilename"

On *nix launch the command:
firefox -no-remote -P secondprofilename

Bingo, now you should have two separate Firefox windows, each running independently of each other. If you click on links in another program, they will probably go whichever Firefox window you opened first. Enjoy. More info.

100 thoughts on “Multiple Firefox Instances

  1. Is there any limit in the number of firefox profiles that can be created?

    My issue is
    I am currently doing selenium webdriver automation in linux for a device. There are 50 devices of same kind and framework will pickup a device depending on availability. I need to by pass unsigned ssl pages. I am using firefox 14.

    I have implemented following but it is not consistent.

    everytime a device is chosen
    adds cer of device to the cert file in firefox profile
    but I am getting sec_error_bad_signature very frequently.

    So I started recreating cert file for every run.

    Now this is posing a problem if multiple devices are run at the same time. Hence I want to create separate firefox profile

  2. Thanks for the good summary how to get multiple profiles running in Firefox. I tried this solution with the PortableApps.com version of Firefox. To get it working with the PortableApps launcher, I needed to copy the FirefoxPortable.ini to the folder where FirefoxPortable.exe resides. In the ini-file I added the -no-remote entry to the AdditionalParameters-attribute.
    Just thought I’d share this solution.

  3. You said that new links “will probably go whichever Firefox window you opened first.” I’m finding the opposite – new links go to either the most-recently used or the most-recently opened, I haven’t figured out which. I would like for new links to go to the first opened — any thoughts since the time of this article on how FF determines which instance to send a new link?

    Not sure if this makes a diff, but in my case, instead of using multiple profiles, I’ve been opening a new tab first, then sending that tab to a new window. This doesn’t give me the auto-start that’s described in this blog, but it gives me much more dynamic control – I only open as few or as many spinoff windows as I need today. But through it all, I want my first instance opened to be the “main” one to which external links are sent.

    Thanks for any thoughts.

    • Which operating system are you using? I found this behaviour to be totally consistent on Ubuntu and OSX. I’d have liked a way to send the link to whichever tab I wanted, but could never get it to work. I’m now seriously considering dumping Firefox because of it’s inordinate CPU usage, so I may soon be a Chrom(ium|e) user.

  4. Pingback: For those who want to run iMacro in parallel but don't have a quick fix.. I found it!

  5. Hi. I am having an issue with my firefox right now. I had it set up to where I could open multiple profiles of firefox at the same time, having the profile manager launch each time I double clicked the desktop icon, but now I can’t get the profile manager to pop up if I currently have a window open. I have to completely close out my current window to get the profile manager to launch. I have went in and added the “-ProfileManager” to the target launch, but it still hasn’t fixed it. Any suggestions as to how to get it to work right again?

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