Assume I am a regular user of website A that forbids multiple accounts. I assume it can identify me with cookies and IP. So if I use a VPN, then open a private tab in my browser, can it still identify me ? The cookies sent to the website will have nothing to do with the old cookies right ? So is this as efficient as using another computer with another connection ?

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    Depending on who you're trying to defend against, have a look at the demo for HSTS super-cookies. It's a bit of a dilemma since fixing it involves a trade-off between security and privacy.
    – tangrs
    Commented Oct 19, 2015 at 11:13
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    What sort of bad design is forbidding multiple accounts from the same IP? Have they never heard of NAT? Commented Oct 19, 2015 at 13:32
  • @Xophmeister The OP didn't say they are forbidding multiple accounts from the same IP, just that they forbid multiple accounts. Commented Oct 19, 2015 at 16:06
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    You might be better off with social engineering - "This isn't eee, this is eee's roommate fff!" - of course, you would also have to use the profiles in a way that was consistent with this story. Always having fff log in one way, and eee log in another way. If you stop at a coffee shop every day, send eee a note from fff saying "dude don't forget julie's coming over tonight, so don't come home bro" etc.
    – corsiKa
    Commented Oct 19, 2015 at 17:59
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    @corsiKa That might not help much if eee and fff make the same spelling mistakes in their respective online rants :) Commented Oct 19, 2015 at 18:07

8 Answers 8


You can not be sure for that without testing because such websites combine more than one technique to identify their users. For example if you use the same computer with a reliable VPN, you still may be identified if the website in question relies for example on browser fingerprinting and/or operating system fingerprinting identification techniques.

Some websites can identify you even if you use Tor browser, VPN ... etc (after suspicion of bad behaviors a user may perform) as they analyze the way how you write.

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    Don't forget the latest dilemma in browser security, HSTS tracking.
    – tangrs
    Commented Oct 19, 2015 at 11:09
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    It is quite fun to visit panopticlick.eff.org - Surprisingly, Chrome's private window had different fingerprint than normal window. Sadly, only real difference was access mode to fonts - so I guess for real algorithm I would be traceable all right.
    – Mołot
    Commented Oct 19, 2015 at 14:04
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    Another new form of tracking is tracking and measuring how you type, no browser, vpn or proxy can change that!
    – matt.
    Commented Oct 19, 2015 at 15:20
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    @enki.dev A browser could add jitter to your keystroke timings, or slow them to a uniform rate (or one of a few uniform rates to handle different typing speeds). Also how is it measured - scripts run locally? This is assuming it's typing timings, as analysis of language used requires a fairly large data set.
    – Chris H
    Commented Oct 19, 2015 at 15:53
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    @ChrisH Correct. There are browser extensions available that just do that. If you're interested in underlying technology, check out behaviosec.com/technology - So, yes, my original comment would be incorrect.
    – matt.
    Commented Oct 19, 2015 at 16:09

"But I'm behind 7 proxies!" It doesn't matter.

Even if you change your IP address, you are still likely giving the website(s) your browser fingerprint. You'll need to use a tool like SecretAgent for Firefox, or write your own.

What you need to do is randomize / disable the following values before they're returned by Javascript:

  1. Screen Size and Color Depth (randomize)
  2. Browser Plugin Details (disable showing / randomize)
  3. System Fonts (disable showing / randomize)
  4. User Agent (maybe randomize)
  5. Cookies (disable)

If you are able to randomize / disable those, like SecretAgent does, it's not likely that you'll be identified by websites / tracking cookies through browser-fingerprinting.

Either that, or you need to disable Flash, Javascript, Java, etc. while browsing. Note that fiddling with the screen size values may break responsive websites, though I haven't tested this.


By 1) using a VPN you are effectively connecting from another IP, and by 2) using a private tab in your browser (or an incognito window, or a different browser altogether) the cookies from your old connection won't be used. So yes, using both will thwart the basic way in which websites identify you.

Note that you might be able to visit the website with a different identity by using #2 alone; VPN might not be needed.

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    Also, be careful of any dropped connection to the VPN. For example in OpenVPN if your connection to VPN server dropped it would revert back to your normal connection which would expose your identity.
    – Paul
    Commented Oct 19, 2015 at 11:36

An incognito window combined with a reliable VPN should indeed hide any correlation between your 2 accounts.

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    You need to explain how/why this is true.
    – schroeder
    Commented Oct 19, 2015 at 18:08
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    I disagree. Even if you change your IP address, you are still giving them your browser fingerprint. You'll need to use a tool like SecretAgent for Firefox, or write your own. Commented Oct 19, 2015 at 19:17
  • I'm guessing this entirely depends on what kind of website we're discussing here. A lot of sites that made it against the rules to run multiple accounts would only monitor for duplicate IP addresses. A VPN (that doesn't spray your real IP everywhere) would bypass that immediately. Incognito windows with multiple browsers is an additional layer of protection. Just out of curiosity, do you know of any sites that try to match accounts based on browser fingerprints?
    – Sevaara
    Commented Oct 23, 2015 at 15:50

You should better use a different browser or at least a real different profile like Firefox offers (Profiles in Chrome share too much). Incognito mode is note enough since some information are shared with this mode and some information are even shared between different browsers.

For deep and extensive information about this topic see Technical analysis of client identification mechanisms.


The best thing is to use a virtual machine with a different OS (Linux/Windows) or different versions (Win7/Win10), if you like a different browser in each (chrome/firefox) and the virtual machine has a firewall rule to only allow connections to the IP of your VPN-Server.

With a big or a second screen, you can run both in parallel and if you don't mix up the focus of the keyboard, you can even pretend to be both persons in chats. But I have seen too many people try and fail, mixing up the names or facts, so I would not recommend it.

If you type just little, try using google translate to one language, then bing translate back to yours, this should add enough differences to make you the foreign exchange student.

However, the general idea is "why would you want to cheat in a browser game?". You gain nothing of value and the impression of being good is tainted by the wisdom that you only achieved it by cheating. It doesn't matter what the rest of the gamers there think, you will know it's not true. You can always ask some of your real friends and invite them to play, way more fun this.


Your browser can be finger printed. Incognito mode will not protect your browsers finger print. Don't believe me go to the website https://panopticlick.eff.org/index.php?action=log&js=yes in incognito mode. Close your browser and open a new one and do it again. It's about the configuration of your browser being unique to your machine. Read their article https://panopticlick.eff.org/browser-uniqueness.pdf and you can learn more about this and how to hide/change your fingerprint.


Please mark this down if this is no longer true and I will delete. But I have built a few apps that stored hostname that was passed via browser. Although this was supposed to be deprecated a long time ago, from the last time I looked, it still passed in all the major browsers.

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    The hostname depends on the connection, not the browser. Commented Oct 20, 2015 at 9:55
  • @A.L - It is a variable stored in your browser. If you were on the same computer using different browsers I could identify you by it. Also your hostname does not depend on your connection. I wish I could double downvote your downvote..
    – blankip
    Commented Oct 20, 2015 at 14:46
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    I didn't downvoted you (I don't have enough rep). Can you please provide an example? Hostname is not linked to the browser. Maybe you're thinking of the user agent? Commented Oct 20, 2015 at 14:49
  • No the hostname variable is captured by browser API. So I can get several things from your browser - your local IP address (and internet IP), your OS, your patches, and hostname.
    – blankip
    Commented Oct 20, 2015 at 15:05
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    Looks like you are referring to the client's hostname. This was possible on really old versions of Netscape for example via Java: java.net.InetAddress.getLocalHostName(). Here is more modern ways to get the IP address: stackoverflow.com/questions/17414972/… Commented Oct 20, 2015 at 16:41

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