[Windows] Open Firefox and Firefox Portable at the same time with TwinFox

One of the coolest things about Firefox is that it’s available in both installable and entirely thumbdrive-based portable editions. If you’re a user of the portable version, however, you might find it annoying that you can’t run the installed version at the same time as the version located on your thumb drive. TwinFox fixes that with just a single click.

What is it and what does it do

Firefox does not like having multiple copies open at once. TwinFox fixes that, allowing you to open the previously installed Firefox copy alongside your copy of Firefox Portable.


  • Lets you run potable Firefox and installed Firefox at the same time
  • Easy to use — just open TwinFox.exe rather than FirefoxPortable.
  • Does not change Windows taskbar icon


  • Requires you to run Portable Firefox, then regular Firefox

Twinfox is a very simple program. In fact, it’s as simple as extracting it to wherever you keep your portable Firefox installation and running it instead of Firefox Portable. Twinfox takes care of all of the hard work, and lets you then open up another instance of Firefox, such as the one installed on your computer.

There’s only one catch with Twinfox. It doesn’t let you open up Firefox Portable after you’ve opened your regular Firefox installation–that is, you must run the portable version first. This is a minor issue, but is still something to be aware of while using the program.

Conclusion and download link

Users of Firefox Portable will absolutely love TwinFox and its ability to open multiple Firefox instances at the same time. Though not very useful for very many people, for those that use or want to use both Firefox’s standard installed profile and their own portable profile, it’s an immensely useful program.

Price: Free!

Version reviewed: v1.0

Supported OS: Windows 

Download size: 311KB

VirusTotal malware scan results: 0/41

Portability: No installation required!

Homepage unknown | TwinFox on Softpedia

[Thanks Eric989!]

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  • RobCr

    You’all should try out Comodo IceDragon
    It is based on FF
    It even has some extra Comodo security that you can turn on.
    What I love about it, is there is a checkbox you can tick (when Installing), that makes it truly portable.
    I have about 10 of them for different categories of browsing.
    The only precaution is don’t run two of them at the same time.
    HOWEVER, you can run any one of them, plus your installed FF, at the same time.

    Regarding my masses of open Tabs, I now just bookmark them when they get too many, and then close them all (As an extra precaution, I export all the saved Bookmarks to a HTML file.)
    FF’s Bookmark manager is very good, and I would be hard pressed to design a better one myself (I was an Analyst for 20 years).

    PS I have learned to hate Chrome, but for those that worship it, Comodo has a portable version called Dragon.

  • Eric989

    I finally got around to using Twinfox and it works great. It can even be used to run multiple instances of Firefox Portable at the same time.

  • Eric989

    @Rob (Down Under): I still haven’t got around to trying twinfox yet, but without it, no matter which Firefox is running first, trying to open the second will open a new window in the already running firefox. To be clear, you will still have the 450 tabs open in one window and you will have one tab open in a second window; it is just like opening a new window in the already open browser. This is different than what it used to do. It used to just pop up a message and say Firefox is already running please close it first. Either way it won’t mess with your tabs.
    One more question about your tabs. Do you just keep FF running 24/7 or do you open them from a bookmarks folder or something? Also, what extensions do you use to manage all those tabs?

  • @Eric989: Sure, certainly can’t kill you. :-P

    I think that’s the only time I’ve ever used that word, except in Switzerland where all the water fountains in Geneve are labeled “Eau potable” or “Eau non potable”.

    @Rob (Down Under): Psst, expect to see that program featured tomorrow ;-)

  • J.L.

    It’s really only limited to memory, imagination, and maybe your drive space.

    Just use multiple profiles: http://kb.mozillazine.org/Opening_a_new_instance_of_Firefox_with_another_profile

  • Rob (Down Under)

    Regarding the 450 Tabs
    A couple of dotTechies have raised quizzical eyebrows regarding my 450 Tabs.
    Years ago I used to be just as slack (lots of open Tabs),
    The older FF did not handle them well. (The new FF is much, much better.)
    Because the old FF used to freeze/crash, I started using the free program URL Gather.
    Brilliant little program, that allows you to categorize and save the URL’s, and allows me to delete the corresponding Tabs.
    The reason that I keep Tabs open, is to remind me to do things. So transferring them into URL Gather, allows me to close the Tabs.
    That worked well, till recently.
    My neighbor works for a council, collecting hard rubbish.
    When he heard that I can fix PCs, he asked could I fix Laptops that he was collecting and disposing into the Council dump.
    I have fixed 3.5 so far.
    The .5 refers to a Dell Inspiron 9400 which has a faulty ‘nearly embedded’ Video card, which is infamous for failing. I have now given up on it, but it still took a lot of work to get it to the point where I then narrowed it down to that problem.
    And life was not easy with the other laptops, as passwords needed cracking, and flippin Group Policy security restrictions made life miserable for me.
    My objective with all that cracking and bypassing, was not to return the laptops to him with cracked OS’s. Rather it was to allow me to install the free program Double Driver (Gizmo’s top choice), to backup the drivers, and then do formats and fresh installs of OS, and then restore the drivers.
    During all that investigation, I had no time to move things into URL Gather. Thus 450 Tabs are open.

  • Rob (Down Under)

    Regarding our discussions on the other dotTech page, I was thinking I would not need both open at the same time.
    However, after reading this page, it occurs to me that I could accidentally open both, and trash my 450 open Tabs.
    So this page is timely, as I could use TwinFox (as described above), to ensure that I never trash my 450 Tabs.
    One question –
    If I accidentally open the installed FF first, and then go to run TwinFox, does it detect the running (installed) FF, and refuse to run ?
    Or does it run, and trash my 450 Tabs ?

    PS Regarding my 450 Tabs, I will explain in a separate post (soon).
    I am concerned that a long post, may be one of the moderation triggers ?

  • AFPhys

    This could really come in handy when checking out whether I wish to update to a new FF version!


  • Eric989

    Thanks for featuring this; that was a pretty quick turnaround as I just mentioned this. I have just one concern. Is it really safe to drink the “Potable” Firefox you mentioned under Pros? LOL