Is Private Browsing Mode Truly Private ?

by Abhishek Bhatnagar on October 11, 2010


Most of the modern Internet browser softwares like IE, Firefox, Google Chrome etc provide  “Private Browsing mode”. In this private browsing mode the Internet cookies are not saved, the browsing history is not maintained and no other data is kept after you close the browser. This is a good relief if you want to browse Internet privately on a shared computer for any reason. But, is this more truly private ? Yes it seems like, because the Internet browsers do the best they can do, but yet there are traces of which websites you opened on your computer.


These traces are not kept by the browser, but kept by the operating systems like Windows, Linux, or MAC OS. These traces are nothing but your DNS cache which is maintained by the OS. It stores which website has what IP address, this is a feature which helps to open websites faster by saving on time which is spent on checking the IP address of a domain using outside name server. Although DNS cache is a good feature to speed up the Internet browsing experience, but it has potential to bust your private Internet browsing. In this article, I will show you how you can see and clear the DNS cache to remove the traces of the websites which you have visited in the private browsing mode.

Display & Clear DNS Cache In Windows

To display the DNS cache of the websites visited on the computer you can follow the below steps :

1. Press “Windows + R” key, this will launch run prompt, type “cmd” and press enter.



2. On command prompt, type “ipconfig /displaydns


this will show the saved DNS records on the screen. If you want to save this list in a text file, you can type the command like “ipconfig /displaydns > file1.txt” , this will create a text file names file1.txt at the path where you execute this command. You can check out the record in the text file later on.

3. To clear the DNS cache, you can simply type the command “ipconfig /flushdns” at the command prompt to clear the DNS cache stored by the Windows OS. This works for all the Window Operating systems including Windows 7, Windows Vista, Windows XP.


Clear DNS Cache In Linux

To clear DNS cache in Linux, open terminal in Linux and type the following command at the terminal

/etc/rc.d/init.d/nscd restart

Clear DNS Cache In Mac OS X and Mac OS Leopard

To clear DNS cache in Mac OS X, open terminal and type the following command

dscacheutil -flushcache

To clear DNS cache in Mac OS Leopard, open terminal and type the following command

lookupd -flushcache

Hope this will help you in a better private browsing experience.

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{ 2 comments… read them below or add one }

Arpit October 11, 2010 at 1:39 pm

Few firefox add-ons stores browsing data, and hence private browsing mode in firefox is totally broken.

More here:

d4knarf2 July 30, 2012 at 12:40 am

I tried this but the dns history in Firefox 14.0.1 is still retained. Why is this?

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