3 ms·

It is normally an image like others have said, however, Google's caching inside gmail is causing some problems: https://blog.mailchimp.com/how-gmails-image-cac

• Grynn 11y ago
  Google merely prevents you from collecting information about the IP address & device. It still lets you know who opened the email. Since the request comes from Google's servers instead of the client device (or browser) you get whatever HTTP headers google thinks are appropriate (and of course the IP address of a Google server) AFAIK Google does not pre-load images (for example, even if no one opened the email Google could request the image). This would destroy open tracking since you'd get a lot of false positives. Since "who" opened is already encoded in the image URL, you still get this info. Anyhew, there's a lot more people do with these tracking images - for example see KickDynamic.com. You can change the image at time of open (to say reflect the user's location, which you deduce from the IP). This can't be done if it's gmail, since you don't have the client's IP. It's kind of strange that Apple doesn't block (or anonymise) images though they're so hot about privacy at the moment.
• tedmiston 11y ago
  FWIW however Intercom tracking email opens seems to circumvent Google's effort. I think it only tracks first open vs. every open though.