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How can they cache tracking pixels? Each one has a distinct URL.

• obmelvin 6y ago
  If I understand your question, the cache GP is referring to is not meant to help across users. Rather, when someone sends you an email the images are pulled into a cache [0]. When you view the email you aren't seeing the resource loaded from the tracking pixel URL, but rather a google cached version. This would mean that the sender wouldn't be able to know about you looking at the email multiple times, etc. [0] I don't actually know if it works that way. Just what I believe the GP is saying. I could maybe see this being done so they can run heuristics on the assets, or something like that.
  • daveslash 6y ago
    I worked for someone back around 2013/14 in which we tried to implement some tracking pixels, and what you described was exactly what we ran into with Gmail recipients. When the e-mail lands in the inbox, Google was retrieving the image from your server, caching it, and then displaying the cached version to the user -- so all you knew was that the email was being delivered to the inbox, but couldn't tell if the email was opened. I don't know if that's how it currently works, but that's what we ran into at the time IIRC.