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I had to know the answer, so I wrote a quick script to test it. It appears that incognito windows can't read cookies from normal windows. I've linked to the sou

I had to know the answer, so I wrote a quick script to test it. It appears that incognito windows can't read cookies from normal windows. I've linked to the source code there. If I've missed anything, let me know. https://cookiechecker.netlify.com/ https://cookiechecker.netlify.com/

richardfeynman 9y ago
So cool that you built that! Here's what Google says about cookies in incognito mode: "If you use Chrome in incognito mode (or in guest mode on Chrome OS), it will not transmit any pre-existing cookies to sites that you visit. Sites may deposit new cookies on your system while you are in these modes; these cookies will only be temporarily stored and transmitted to sites while you remain in incognito / guest mode. They will be deleted when you close the browser, close all open incognito windows or exit guest mode." Source: https://www.google.com/chrome/browser/privacy/archive/20140826/index.html https://www.google.com/chrome/browser/privacy/archive/201408... I first noticed that FB might be able to detect sites you visit while in incognito mode when I noticed that I was personally being retargeted by sites I visited in incognito mode while on Facebook. Here's an interesting quora thread I found while looking into it: "Also the cookies act too important role here. Cookies during Incognito Mode are saved in temporary folder, and they get purged after session ends. But when browsing Facebook and Google in the same session, they both share same cookies folder and cookies help to send tailored ads to users." https://www.quora.com/Im-using-Incognito-mode-for-Google-searching-but-Facebook-still-shows-ads-relevant-to-my-searches-How-is-that-possible https://www.quora.com/Im-using-Incognito-mode-for-Google-sea... Curious for your take.
richardfeynman 9y ago
"It appears that incognito window can't read from cookies from normal windows." To be clear, the claim I'm making is that normal windows can read cookies from incognito windows.
- tlb 8y ago
  A simple test suggests otherwise, using Gruez's recipe above but swapping the private and non-private windows. There are potential information leaks, such as the combination of IP address, user agent, screen size, and fonts available. And there may be bugs in 3rd party plugins like Flash that fail to respect private mode. But it doesn't seem to be anything as simple as cookies being shared.
  - richardfeynman 8y ago
    Thanks. If they're not using the temporary cookies folder, I'm curious how Facebook shows ads based on incognito browsing. Some form of device fingerprinting?

richardfeynman 9y ago

So cool that you built that! Here's what Google says about cookies in incognito mode: "If you use Chrome in incognito mode (or in guest mode on Chrome OS), it will not transmit any pre-existing cookies to sites that you visit. Sites may deposit new cookies on your system while you are in these modes; these cookies will only be temporarily stored and transmitted to sites while you remain in incognito / guest mode. They will be deleted when you close the browser, close all open incognito windows or exit guest mode." Source: https://www.google.com/chrome/browser/privacy/archive/20140826/index.html https://www.google.com/chrome/browser/privacy/archive/201408... I first noticed that FB might be able to detect sites you visit while in incognito mode when I noticed that I was personally being retargeted by sites I visited in incognito mode while on Facebook. Here's an interesting quora thread I found while looking into it: "Also the cookies act too important role here. Cookies during Incognito Mode are saved in temporary folder, and they get purged after session ends. But when browsing Facebook and Google in the same session, they both share same cookies folder and cookies help to send tailored ads to users." https://www.quora.com/Im-using-Incognito-mode-for-Google-searching-but-Facebook-still-shows-ads-relevant-to-my-searches-How-is-that-possible https://www.quora.com/Im-using-Incognito-mode-for-Google-sea... Curious for your take.

richardfeynman 9y ago

"It appears that incognito window can't read from cookies from normal windows." To be clear, the claim I'm making is that normal windows can read cookies from incognito windows.

tlb 8y ago
A simple test suggests otherwise, using Gruez's recipe above but swapping the private and non-private windows. There are potential information leaks, such as the combination of IP address, user agent, screen size, and fonts available. And there may be bugs in 3rd party plugins like Flash that fail to respect private mode. But it doesn't seem to be anything as simple as cookies being shared.
- richardfeynman 8y ago
  Thanks. If they're not using the temporary cookies folder, I'm curious how Facebook shows ads based on incognito browsing. Some form of device fingerprinting?