Firefox 3.5 and Privacy

One of the major themes in Firefox 3.5’s user interface is a focus on privacy. So far Firefox’s approach to privacy has been essentially all or nothing. Users previously had the ability to easily clear all of the data the browser had stored about them, but this destroyed absolutely everything. Instead of being able to go off the record, this was kind of like shooting the reporter. Now users have considerably more control over their privacy, both proactively and retroactively.

There are 5 new privacy features introduced to Firefox with the 3.5 release. Here is a description of how each one works:

Tools > Private Browsing (Proactive Privacy)

If you would like to browse the Web without Firefox recording history, Private Browsing allows you to quickly launch a browsing session that will be completely off the record:


After launching into private browsing mode, you receive a confirmation explaining that Firefox isn’t going to remember anything:


It’s great to get private browsing mode into a shipping copy of Firefox, since private browsing mode was previously both targeted and canceled for Firefox 3 (and in the interim it was added to IE and Chrome, which is really great for users). Private browsing mode actually has a long history of not quite making it into a final release, way back in 2002 Blake and Asa prototyped it for Netscape. We all owe a huge thanks to Ehsan Akhgari who worked incredibly hard to get the feature fully implemented.

Tools > Clear Recent History (Retroactive Privacy)

Let’s say that you’ve been browsing around the Web for awhile, perhaps shopping for an engagement ring, or researching a medical condition, and you realize that you really should have been in private browsing mode. The Clear Recent History feature is kind of like Private Browsing, except it works in reverse. (All good interfaces support undo!)


After selecting Clear Recent History, you will be asked what time period you would like to erase:


If you expand details you can see the somewhat arcane list of things being removed, but the short version is that “history” refers to everything that is implicitly collected by Firefox as you browse the Web (and we really mean everything). You can also use this dialog to max out the time range and effectively reset Firefox, similar to the old dialog.

Thanks go to Drew Willcoxon, Shawn Wilsher and Johnathan Nightingale for implementing this feature.

History > Forget about this Site (Retroactive Privacy)

If you don’t want to clear a specific time range but would rather selectively delete items out of your history, Firefox now offers the ability to remove all of the history of a particular Web site. For instance you can select this article in your history (either through the Library window, or the History Sidebar), and then use “Forget About this Site” to remove every visit to


This is a bit more powerful than deleting individual visits if you are interested in pruning your history. This feature was implemented by Shawn Wilsher.

Simplified Privacy Options (Proactive Privacy)

We’ve also significantly simplified Firefox’s privacy options. By default Firefox will remember where you go on the Web:


However, if you are extremely privacy conscious, or you are setting up a computer that will be in a public location and used by many different people, like a hotel lobby or a computer lab, you can now very easily set Firefox to never remember history. This is basically the same thing as always running Firefox in private browsing mode, except that the mode is always on.


Of course if you have previously changed your history settings, or are interested in micromanaging exactly what Firefox will and will not store as you browse the Web, the full range of settings are still available:


This feature was implemented by Ehsan Akhgari.

Ability to Control What Appears in the Location Bar Search Results (Proactive Privacy)

When we expanded the capabilities of the location bar to search against all history and bookmarks in Firefox 3, a lot of people contacted us to say that they had certain bookmarks they didn’t really want to have displayed. In some cases users had intentionally hidden these bookmarks in deep hierarchies of folders, somewhat similar to how one might hide a physical object. Having something from your previous browsing displayed to someone else who is using your computer (or even worse) to a large audience of people as you are giving a presentation, is really one of the most embarassing things that Firefox can to do you. So now in Firefox 3.5, users have complete control over what types of information are displayed in the location bar (or suggestions can be turned off entirely):


This feature was implemented by Ed Lee and Dietrich Ayala.

Even More Control!

But what if the five privacy tools described above still aren’t enough? You want to be able to save both bookmarks and history, but in a way that only you can access the information.

The most direct way to do this is to create a new user account in the operating system you are using, and to give it a password. Firefox will create a separate profile for that user, and you can use this new profile to store bookmarks and history.

Alternatively, you can launch Firefox and display the profile manager. This is a feature that is intentionally hidden from the normal Firefox UI, since it is a bit more complicated than creating a new user account in your operating system, and is more commonly used by developers who are testing Firefox. Instructions for accessing Firefox’s profile manager vary by operating system, but we have a detailed article explaining the feature.


The third, and perhaps most extreme way to keep your bookmarks and history private, is to use something called Portable Firefox. This allows you to put both Firefox and your profile onto a USB thumb drive. You can then place the thumb drive into a physical box, and literally lock it, bury it, etc.

What’s Next?

While Firefox’s profile manager is currently more of a tool designed for developers, with emerging tools like Mozilla Lab’s Weave, users may soon be logging into their Web browsers to access all of their personal information. The great thing about this is that similar to Web mail and other online services, users can create multiple accounts. Also (unlike Web mail and most other online services) Mozilla Lab’s Weave encrypts all of your information, so you can be assured that you are the only one who has the ability to access it.

Firefox takes your privacy incredibly seriously, and we hope that you enjoy using all of the great new features we’ve added in Firefox 3.5, which is available for download starting today!


  1. While I’m all for extolling the virtues of using the profile manager, keep in mind that it’s officially an unsupported feature [1] and therefore could be broken at any time without a fix guaranteed.


  2. Thanks Alex. The new features are finally nudging me towards going back to Firefox (from Safari). Also, I had never heard of Portable Firefox. Too bad it’s not an officially supported Mozilla product (and with a Mac version that does not require Wine).

  3. Two things in Private Browsing mode could be better:

    1) I really liked the “Black Location Bar” mock-up, which you painted 2 years ago:
    Also, on such black location bar there should be placed noticeable (red?) button: “Quit Private Browsing”.

    2) When Private Browsing is starting, Firefox unloads everything (all my 50 open tabs, etc.), actually, it is almost restarting into some special built-in “empty” profile. Google Chrome does it better: it opens a SECOND window for private browsing, leaving non-private window untouched.

  4. Beta Capricus

    I have to agree that Firefox closing my dozens of tags temporally to start a new private session puts me of enough that I’ll just keep just opening chrome if I want to browse privately. Hope this feature keeps getting refined user-friendliness wise in upcoming versions. Also, what ever happened with that “unless bookmarks are tagged with” modifier for location bar options that I saw in a mock-up a few months ago? ( I really digged that feature, and was hoping it could make the final cut. If only to speed up my awesomebar by excluding some of my less useful but huge bookmark directories.

  5. Unfortunately, when you have up to 200 tabs open (this happens to me sometimes), the only practically useful way of private browsing, is to minimize Firefox window (never use it’s private browsing), and start another browser (Safari, Chrome, Opera, …), which is specially configured to never save any history. And when finished, close it, and return to Firefox window… This method is practical. It much faster, because it avoids reloading of all Firefox tabs.

  6. I also prefer Chrome’s dual-window private mode option – it allows me to leave a whole session open and usable while having private mode running at the same time.

  7. You know, I thought I was following all of this pretty closely, and I have been using nightlies the whole time, but much of this is completely new to me. Really great features.

    I do have to agree with everyone else about how it closes all of the current tabs to enter private mode. Chrome’s method of using a new private window seems much better. In situations where I want to leave my tabs open, at least the retroactive privacy options will work nicely.

  8. Semi-Portable Firefox.
    I am interested to something like “Portable Firefox” installed on my hard disk in a partition other than C: . Does it exist ? Advantage : if Windows has an hard crash that need format of C: and reinstallation, this “new Firefox” will survive. The program and user data may be separated to need only 1 occurrence of the program if there are several users.

  9. Sebastian Krämer

    I think you could extend the private browsing by optionally using a tor proxy, if configured.

  10. Alex, is a privacy extension along the lines detailed in this proposal feasible within the current privacy infrastructure of Fx3.5?

  11. I agree with others about it not closing the current window. I also like some of the things people brought up that were cut, like the black location bar (or some better visual cue) and the hide tag.

  12. You wrote:

    Firefox takes your privacy incredibly seriously (…)

    I strongly disagree with this claim. Firefox with each release adds more and more privacy invasive features. For example, in Firefox 3.5 there is, aside from so-called “safebrowsing” added in previous releases, another Google service integrated – geolocation. I don’t think that you can claim that “Firefox takes your privacy incredibly seriously” while at the same time browser supports superflous unique identifier (aka “reinvented cookie” as Gavin aptly described it).

    Of course, so-called Google’s “safebrowsing” is much more privacy-invasive than geolocation – apart from sending unique identifier with almost each connection related with “safebrowsing” (in wrkey parameter) there is also a possibility for Google in some cases to gather information about visited URLs. See my demo (written more than half a year ago – it works with all Firefox versions starting from 3.0; for versions >= 2 and < 3.0 there is another demo). It also works with “private mode” enabled.

  13. I agree with ” BartZilla ”

    I had 3.0 “shoved down my throat” when I did not upgrade from 2.0.
    First thing I noticed was “unauthorized” changes to my bookmarks.
    My favorite search engine was replaced with
    “Google”! and Google was installed in my browser!
    “Everyone” knows that Google has cut a deal to supply the Government with information they gather on “all” computer users surfing habits & subjects.

    So Mozilla is carrying water for Google,that means that Mozilla is now helping in the collection of data on all of us.

    I no longer recommend Mozilla to anyone.

    Just what I need,…to look up information on adult diapers for my parents,and Mozilla tells Google they are for me!
    Anyone doing business with Google will not be doing business with me.

    Good Bye Mozilla.

  14. I agree with BartZilla too.

    In Firefox 2.0 there was an option to use a “DOWNLOADED LIST of suspected sites” (see screenshot):
    but it is gone in Firefox 3.0! Now you have no choice, there is only one option left, which was called “check by asking [Google]” in Firefox 2.0, and now it is renamed to “Block reported attack sites” and “Block reported web forgeries”. Note, that “Google” name is dropped, so uninformed users can’t even KNOW that Google tracks all their traffic! Too bad. This is WRONG. Ability to use a “downloaded list” should be returned! Free Firefox!

    Currently, Google tracks EVERY webpage you are viewing in Firefox 3 (!), but it CAN be disabled:


    1) Navigare to “Tools / Options / Security”.
    2) UNcheck “Block reported attack sites”.
    3) UNcheck “Block reported web forgeries”.
    4) Click “OK” button.

  15. I just downloaded 3.5, but my bookmarks were filled with sites I deleted a long time ago. I was able to restore my current list of bookmarks, but it really bothered me that Firefox was able to restore those bookmarks. How can I wipe out my old bookmarks for good?

  16. Mr. Faaborg,

    is the in-private browsing somewhat new for firefox? i switched from using explorer because i did not want in-private. when i switched I’m pretty sure this wasn’t an option. can you tell me how to block it completely. i do not want this feature.

    please help,


  17. Fay: If you are concerned about children having access to private browsing mode, you can use a fee extension like that modifies Firefox to remove features like private browsing mode, and only allows access to 2.5 million sites that have been pre-approved by teachers and other parents. KidZui is great, as far as Web browsers designed for kids, I think KidZui built on top of Firefox is pretty much the best out there right now.

  18. Thanks for the information. I always use Firefox. Only lately I’ve got a little bit disappointed with it. The last version gets to much RAM. But I hope I’ll correct is soon.