Does email tracking use a post request or a get request?

Question

My understanding of email tracking is that there is an invisible 1x1 pixel image embedded in the email. What I don't quite understand is how how does that pixel help track if an email gets opened or not. I've been told that a GET request is performed, but how does that work? Which party performs the GET request and when is it initiated?

Answer 1

Does email tracking use a post request or a get request?

Embedded images (HTML <img> tags) are always retrieved using GET requests.

The exact request type is not actually important, though. Web servers are technically able to track received GETs (e.g. log the request, store something in a database) equally as well as they can track POSTs.

Which party performs the GET request

It works literally the same way as images in websites. If you're viewing the message in your browser, then the image is retrieved by the browser (just like on an ordinary website).

(There are exceptions, e.g. if you open a message in Gmail, then all embedded images are first downloaded by Google servers and only then provided to the browser.)

Similarly, if you're viewing the message in a mail app, then all linked assets are retrieved by the mail app.

and when is it initiated?

As soon as the recipient's mail app needs to display the images. This could be as soon as the message is opened or even previewed.

Note that unlike browsers, most mail apps actually ask whether the reader wants to download embedded images – precisely to prevent tracking from happening. So in most cases, the tracking pixel won't be loaded until you press "Allow images from this sender" or something like that.