Firefox's per-window Private Browsing mode coming soon

Martin Brinkmann
Aug 9, 2012
Updated • Aug 9, 2012

I'm not sure which browser implemented the so called private browsing mode first, but what is clear is that all major browser developers must have thought that it is a good idea as it is now a feature in all of them. The implementation on the other hand differs a lot. You can for instance spawn multiple incognito windows in the Chrome browser without affecting other open windows and tabs in the browser, while Firefox users on the other hand were not that lucky up until now. When you start the private browsing mode in the browser, all other windows and tabs get closed, which means that you start with a single blank window and nothing else.

And since we like all browsers here: Opera users can comfortably open private tabs in the active browsing window, while Microsoft's Internet Explorer uses the same methodology as Google's Chrome browser.

When you open the private browsing mode in Firefox, for instance with a click on the Firefox button and the selection of Private Browsing Mode from the menu (or by using the shortcut Ctrl-Shift-P), you will notice that all existing windows of the browser get closed, and a new blank window gets opened that is informing you about the mode you have just entered.

All private browsing modes have in common that the browser does not record the browsing history for the tabs or windows that you open in private browsing mode. Websites you open do not get added to the browsing history, the web form history, temporary internet files or cookies do not get stored permanently as well.

And while it is not a 100% anonymous mode, as Internet servers and your ISP may still track what you are doing on the Internet, it is an effective solution to avoid this from happening on the local computer. It can be helpful if you are at a friend's house and want to use the computer to check your email account, or if you want to do the same on a public PC.

Mozilla's implementation so far has been far from optimal, and ever since the feature had been introduced in the browser, a request was made to switch from the all or nothing approach to a per-window approach instead that browser's such as Chrome or Internet Explorer are already offering.

Why a per-window private browsing mode and not a tab-based private browsing mode like that of the Opera browser? Mozilla believes that it is too difficult (for users) to keep an overview of private browsing tabs and regular tabs. Up until now, code prevented Mozilla from implementing a per-window private browsing mode. If you look at the Bugzilla listing linked above, you will notice many dependencies and blockers that prevent the feature from being implemented.

Josh Matthews, who is the lead currently working on resolving the dependencies seems to be making good progress, and while there is no fixed date yet for the implementation of per-window private browsing in Firefox, it is certain that it is coming sooner than later.

Which private browsing mode do you favor and why? Or are you someone who does not use the feature at all? (via Techdows)


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  1. mikkle said on November 11, 2012 at 7:39 pm

    Firefox’s private browsing mode can disrupt one’s entire workflow. It doesn’t make sense to defend their current implementation by belittling the user, saying that they can’t keep an overview of private and non-private tabs. It’s especially easy if you do what Chrome does by opening a new private window with its own distinctive theme.

    I wish Firefox would implement this already. It’s hard not to switch to a browser that does it better.

  2. Firefoks! said on October 2, 2012 at 4:06 am

    Also, I thought the spy logo in chrome incognito mode very cool, then I just realized right now, the masquerade logo from FF is also very very cool!

  3. Firefoks! said on October 2, 2012 at 4:03 am

    Yes yes yes. Finally this is coming. It is pretty much the only reason why I kept 2 browsers, ff+chrome, in my computer. I exclusively use everything Google provides, their OS, their services, etc., except for the browser. I JUST LOVE FIREFOX.

  4. test112 said on September 7, 2012 at 10:05 pm

    At the moment I uderstand that current status is, that it should be Tab based. I have FF private mode turned on from preferences. When I have logged on into my gmail account, I open a new tab and from there I go to google docs website – it gets logged on without credentials! So it is not TAB based at the moment?

    1. Martin Brinkmann said on September 7, 2012 at 10:12 pm

      Private browsing mode is browser based at the moment.

      1. test112 said on September 8, 2012 at 10:55 am

        OK, thx. Lets wait for futere version then…

  5. Zu download said on September 6, 2012 at 9:28 pm

    I think firefox should update their sync function, I use both firefox and chrome, and I love chrome sync function, it’s easier than firefox’s, quick and you can do all it with 1 gmail.

  6. Josh Matthews said on August 13, 2012 at 8:30 pm

    Unfortunately, the full-time developer hasn’t materialized, so it’s still just me and a couple other volunteers grinding away in their spare time. Progress is being made, but I’m not optimistic that this feature will be finished “soon”. That is, unless other people want to help! has more information on how to get involved; I’m particularly looking for people who can write Javascript (yes, Firefox is written in JS, who knew?). Get in touch!

  7. Matias S. Aquino said on August 12, 2012 at 4:01 pm

    Martin, Opera can do both private tab AND private window, at the same time! (Opera > Tabs and Windows > New Private Tab / New Private Window) Obviously, you do not lose the tabs you have already opened!

  8. ComicHippo said on August 9, 2012 at 7:02 pm

    Is there a way to start Firefox directly into private mode ? Can you also tell how to do that on other browsers ? BTW you can make it your next blog post :-)

    1. Martin Brinkmann said on August 9, 2012 at 7:17 pm
      1. ComicHippo said on August 9, 2012 at 7:25 pm

        Thanks .

  9. Gary said on August 9, 2012 at 11:19 pm

    That’s a huge amount of blockers & dependencies. It’s going to be at least a couple years before those get cleared.

    1. Caspy7 said on August 10, 2012 at 1:17 am

      (FYI all of the dependencies with slashes through them have been closed.)

      In the bug, one of the last few comments (#91) one of the developers replies to the question of ETA saying that there is another developer who will now be working on the feature full-time and that: “Almost all of the big dependencies have either been fixed already or have patches, so my guess would be “soon”.”

      Perhaps this comment or something connected to it accounts for Martin’s optimism.

  10. Karl Gephart said on August 9, 2012 at 10:59 pm

    In the meantime, I’ve been quite pleased with the firefox add-on, “Private Browsing Windows”… I’ve dragged the “mask” icon from the add-on bar (through the customize option) up to my toolbar just to the right of my “movable” firefox button. Clicking on the mask icon easily opens another browser window (not tab) for private browsing.

  11. Andre said on August 9, 2012 at 8:26 pm

    By far, Opera’s approach. It’s the most flexible mode… But I would already be satisfied if Firefox could offer Chrome mode

  12. PixelWizard said on August 9, 2012 at 8:01 pm

    By my choice, only one Firefox window is allowed on my system – can’t have a second on in private mode as Jim apparently does. So a change to allow per-tab privacy sounds good to me.

  13. MikeL said on August 9, 2012 at 6:56 pm

    I like Chrome’s way of doing it too. I actually don’t like very much at all Firefox’s, current, way of doing it either, entire browser in private browsing mode, period. Glad this change is coming to Firefox, hope it lands soon.

  14. Jim said on August 9, 2012 at 6:36 pm

    I like Mozilla’s approach on this one. I think having separate windows for private browsing and regular browsing sessions would make them easier to keep track of, especially if you’re one of those folks that likes to have a lot of sites open all at once.

    That said, I often use Opera and haven’t had any problems keeping track of private tabs due to the little icon they put on the tab.

    1. anony said on August 10, 2012 at 7:48 pm

      And Opera can do both.

      Man, what took them so long anyway? Been always annoyed when I have to close normal tab to use private browsing on FF.

  15. OSS said on August 9, 2012 at 6:07 pm

    Thanks for the article. A small typo: should read “Mozilla believes that it is too difficult” not “too difficulty”:)

    1. Martin Brinkmann said on August 9, 2012 at 6:51 pm

      Thanks, corrected.

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