I use a private IE window to browse facebook (theoretically no data stored locally). I log in to facebook maybe once every 6 months.

Two months ago, I used Chrome on the same machine to search for Dell computers, a specific model.

Both searches were done on the same network.

I logged in to facebook today, and lo and behold, ads for that specific Dell model (far too specific to be random). How did facebook get this information? Is my internet provider selling all my search history? Is there some other mechanism that I don't know? I thought browser data was isolated.

  • Ads on Facebook are not from Facebook, but from ad networks.
    – schroeder
    Aug 11, 2019 at 15:59
  • @schroeder In that case, how are they identifying me? My understanding is that there is a way to ID a browser session by resolution, version, and a few other params, but across browsers?
    – VSO
    Aug 11, 2019 at 16:00
  • But you are logging into Facebook, right? So you are identified in that way. It will depend on how you did the search and what you were logged into on Chrome to know how the connections could legitimately be made.
    – schroeder
    Aug 11, 2019 at 16:01
  • @schroeder Ah, so by email? Got you. The funny thing is that I am not logged into Chrome with any of my personal accounts, ever, but I can see how it would tie to my name and so on.
    – VSO
    Aug 11, 2019 at 16:10
  • Are you friends with a colleague on FB? Potentially someone who did research the server model by ways visible to FB? Do you have a professional or "strong" relationship to that person know to FB? Welcome to the world of AI.
    – Mantriur
    Aug 11, 2019 at 21:05

1 Answer 1


The answer to your question is "Super cookies"
The trick is about HTTP Strict Transport Security (HSTS) for something it wasn't intended for.
HSTS is a modern web feature that allows a website to tell a browser it should only connect to the site over an encrypted connection.

Which makes the cookies for that website work even when you're in icognito mode.
For more information read those references:

Ref_1 | Ref_2 | Ref_3

This Answer is for your question

"Is there some other mechanism that I don't know?"

But regarding your ISP, I think things are more terrible than storing a cookie :D
And about your question:

"How did facebook get this information?"

The Method i Told you about. And never forget that facebook stores the search history in their database, so that also may be used in advertisements so make that in mind too.

  • What search history?
    – yeah_well
    Aug 11, 2019 at 17:10
  • 1
    He said he used IE for FB (yeah, dunno), but the search was in Chrome. Fingerprinting seems more likely, albeit also a bit of a stretch across browsers. More often than not, it involves connecting actions not necessarily apparent. I talked to a friend during a stroll about a very specific and niche product. Couple of days later I saw ads for it on Facebook. Initially I suspected his cellphones, but let's get real. He likely googled it with a Facebook cookie, we're friends on FB and work in the same related industry, 1+1. More often than not, there's an obscure rather than a complex answer.
    – Mantriur
    Aug 11, 2019 at 20:59
  • 2
    Super cookies don't work across browsers. Do you have any evidence to suggest Facebook is using HSTS super cookies?
    – Anders
    Sep 10, 2019 at 18:28
  • Apple has put measures in place to prevent this type of HSTS abuse in its Safari web browser (webkit.org/blog/8146/protecting-against-hsts-abuse). Does anyone know if other browsers (e.g. Firefox, Chrome, IE) have done the same?
    – mti2935
    Jan 8, 2020 at 18:07

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