How-To Geek

How Private Browsing Works, and Why It Doesn’t Offer Complete Privacy


Private Browsing, InPrivate Browsing, Incognito Mode – it has a lot of names, but it’s the same basic feature in every browser. Private browsing offers some improved privacy, but it’s not a silver bullet that makes you completely anonymous online.

Private Browsing mode changes the way your browser behaves, whether you’re using Mozilla Firefox, Google Chrome, Internet Explorer, Apple Safari, Opera or any other browser – but it doesn’t change the way anything else behaves.

What Browsers Normally Do

When you browse normally, your web browser stores data about your browsing history. When you visit a website, your browser logs that visit in your browser history, saves cookies from the website, and stores form data it can autocomplete later. It also saves other information, such as a history of files you’ve downloaded, passwords you’ve chosen to save, searches you’ve entered in your browser’s address bar, and bits of web pages to speed page load times in the future (also known as the cache).

Someone with access to your computer and browser could stumble across this information later – perhaps by typing something into your address bar and your web browser suggesting a website you’ve visited. Of course, they could also open your browsing history and view the lists of pages you’ve visited.

You may be able to disable some of this data collection in your browser, but this is the way the default settings work.


What Private Browsing Does

When you enable Private Browsing mode – also known as Incognito Mode in Google Chrome and InPrivate Browsing in Internet Explorer – your web browser doesn’t store this information at all. When you visit a website in private-browsing mode, your browser won’t store any history, cookies, form data – or anything else. Some data, like cookies, may be kept for the duration of the private browsing session and immediately discarded when you close your browser.

When private-browsing mode was first introduced, websites could get around this limitation by storing cookies using the Adobe Flash browser plug-in, but Flash now supports private browsing and won’t store data when private-browsing mode is enabled.


Private browsing also functions as a completely isolated browser session – for example, if you’re logged into Facebook in your normal browsing session and open a private-browsing window, you won’t be logged into Facebook in that private-browsing window. You can view sites with Facebook integration in the private-browsing window without Facebook tying the visit to your logged-in profile. This also allows you to use the private-browsing session to log into multiple accounts at once – for example, you could be logged into a Google account in your normal browsing session and log into another Google account in the private-browsing window.

Private browsing protects you from people with access to your computer snooping at your browsing history – your browser won’t leave any tracks on your computer. It also prevents websites from using cookies stored on your computer to track your visits. However, your browsing is not completely private and anonymous when using private-browsing mode.


Threats On Your Computer

Private Browsing prevents your web browser from storing data about you, but it doesn’t stop other applications on your computer from monitoring your browsing. If you have a key logger or spyware application running on your computer, that application could monitor your browsing activity. Some computers may also have special monitoring software that tracks web browsing installed on them – private browsing won’t protect you against parental-control-type applications that take screenshots of your web browsing or monitor the websites you access.

Private browsing prevents people from snooping on your web browsing after it’s occurred, but they can still snoop while it’s occurring – assuming they have access to your computer. If your computer is secure, you shouldn’t have to worry about this.


Network Monitoring

Private browsing only affects your computer. Your web browser can decide not to store browsing activity history on your computer, but it can’t tell other computers, servers, and routers to forget your browsing history. For example, when you visit a website, the traffic leaves your computer and travels through several other systems to reach the website’s server. If you’re on a corporate or educational network, this traffic goes through a router on the network – your employer or school can log the website access here. Even if you’re on your own network at home, the request goes through your Internet service provider – your Internet Service provider can log the traffic at this point. The request then reaches the website’s server itself, where the server can log your access.

Private browsing doesn’t stop any of this logging. It doesn’t leave any history lying around on your computer for people to see, but your history can always be – and usually is — logged elsewhere.


If you really want to browse the web anonymously, try downloading and using Tor.

Chris Hoffman is a technology writer and all-around computer geek. He's as at home using the Linux terminal as he is digging into the Windows registry. Connect with him on Google+.

  • Published 06/30/12

Comments (17)

  1. wat

    Am I the only person in the world clean browser cache everyday ?

  2. blind

    Google Chrome Incognito doesn’t work Zoom pages by default (((

  3. Kodess

    @wat: No I have a friend that does that. Very annoying, google searches are lost etc etc, and cleaning the cache everyday doesnt make your computer faster, nor does the cache take up much space.

    I only really use private browsing when I am searching for presents for family members, planning surprise parties or browsing for things for my secret love of salsa dancing :3

  4. Dean


  5. Fr0stbite

    I prefer leaving the cache as it is.It helps loading pages faster.With 4 GB of RAM and 600 GB of HDD space,who needs any cleaning.Incognito basically removes any browsing history done during the session.I would rather use proxy sites than Tor.

  6. cam2644

    It’s also a good idea to remember to log out of Google etc when not using it to stop your searches being tainted

  7. rbouvet

    I know there isn’t any one magic bullet for online surfing, and one can only
    chose which browser works for them. But for me, I enjoy using
    Comodo Dragon in ‘private mode’ when I want to leave as tiny a footprint
    as possible.

  8. Thomas

    I use Chrome and I always clean unnecessary cookies by Vanilla Cookie Manager. It’s really increase your privacy and prevents some web sites like Google to track you :)

  9. Rod

    I tried using TOR once because I was just curious and I used it for some light web surfing, I decided to look up some desktop wallpapers and I got to a site and it said that the TOR IP address was banned for uploading illegal content.

    I never used TOR again.

  10. Anonymous

    Using a “proxy” like TOR will help you be more anonymous online. But the routes that TOR sets up are usually through some pretty slow “nodes” which basically slows your whole connection down. Last time I tried it, quite a bit of my hops were through middle Africa! I mean, do they even have Internet in the Congo?

    So if you really want to be more anonymous, try changing your MAC and IP addresses (which can be done on the fly), setting the browser agent to something other than what it is, use a proxy like TOR and then make sure to run your browser in private mode while connected to a public WiFi hot spot. You might also not want to use Windows since there are ways Microsoft can tell who you are even though they “don’t keep any personal identifiable information about you”!

    Thinking of breaking the law or terrorizing someone are you? DON’T! I still left out a few other considerations that might expose your online anonymity. (See if you can figure it out.) About the only thing you can do if you’re really intent on being anonymous might be to steal a computer, illegally connect it somewhere that you’ve never connected to (and has no record of you) and then do your dirty business that way. But chances of you getting caught are still pretty good. So again, DON’T do it!

    P.S. I may be obsessively clearing my cache and posting anonymously, but I do realize that it wouldn’t be too hard for someone to really find me either. (I’m not breaking the law, I just hate telemarketers and spam/bacn!)

  11. Anonymous

    If your using Firefox you can set it to delete your history and everything else when you close it if you don’t want anyone looking at what you’ve been doing.

  12. TheFu

    Being anonymous on the internet isn’t very simple. Tor is part of the answer, but if you’ve ever used the same login on the PC, you are probably still leaking identifiable information. Let me see if I can find the steps to be anonymous ….

    If I wanted to be anonymous and not be caught, I’d do these things …
    a) spoof the physical MAC address on the PC
    b) run a virtual machine; I’d setup a new install using defaults for everything.
    c) spoof the physical MAC address inside the virtual machine (is this a virtual MAC?)
    d) use a fresh, brand new, account with a browser that has never been used for anything else. NEVER.
    e) use TOR

    Then I’d use someone else’s network, NEVER my own – NEVER. The network used would need to be:
    a) not covered by cameras – not an open business
    b) not prone to intensive logging
    c) probably not on a well driven road with other business or traffic cameras.

    Finally, I’d use a new account on the website – never before used anywhere.

    All of these things are necessary. Missing any one and you seriously risk discovery. Using just TOR alone does not make you anonymous, it just encrypts your traffic so your ISP can’t see it. The last TOR node you leave onto the real internet sees everything. That’s why intelligence agencies around the world run TOR nodes. All the major country intelligence agencies do this.

    IE used to write every URL visited to a hidden file that was never shown to users – not power or administrative users either. I think this was added to help law enforcement. This file was separate from the browsing history and other files we all know.

    Honestly, private browsing is a joke. There are leaks found all the time. It might be good enough to fool a girlfriend or mother, however.

  13. rg

    Boot off live Linux CD . No HDD boot. Ever. Better , remove HDD.
    Change Mac.
    Use DNS crypt of open DNS
    Use a VPN like Packetix

  14. SatoMew

    A safer way of using Tor is through Tails, which is a Linux distro made with anonymity and encryption in mind. You obviously boot to it from a Live CD, Live DVD or Live USB, which helps leaving less traces of your activity on the PC. The only way there could still be leaks would be if the RAM isn’t cleared when you boot off from it but I believe that those cases are rare, albeit possible.

    Also, don’t use Google if you want anonymity. Use DuckDuckGo or any similar alternatives.

  15. Citrus Rain


    ISP can catch you though DuckDuckGo, Google encrypts the data so the ISPs can’t figure out what you’re doing.

  16. Tony

    For the n00bies out there, this is also known as “Porn Mode”.

  17. spike

    @wat: I normally do, too.

    @Fr0stbite: Cleaning isn’t just for disk space.

    (the first)Anonymous and TheFu explained well, although for most people’s purposes, these practices are overkill… only necessary when doing something you shouldn’t, so don’t. :-)

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