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Comment by xnx | Hacker News Reader

Gmail does. This is great for privacy because it destroys the usefulness of the tracking pixel to the marketer.

Eh... Not really... It's pretty easy to generate a unique image url per customer and use that to determine whether a customer opened the mail or not and it's about the same cost as a traditional tracking pixel, complexity-wise.

Indeed, the three email tracking services I'm familiar with (HubSpot, Yesware, and Outreach) all generate unique URLs per recipient. The only information you don't get for Gmail clients is location, but you get the most valuable info which is if/when/how many times the email is opened.

I remember reading that gmail caches these images, rendering the how-many-times useless.

GMail absolutely caches images. The cache is primarily for performant delivery of data over mobile networks though and reduced load of repeat same-day viewing, and less for privacy.

While their cache is large, it's not infinite. If what you're interested in is whether a customer engages with an email multiple times over a few days, you'll likely get the pixel hits to confirm it over that time period. Of course, as you imply, you wouldn't be able to collect how many times an hour a single customer has viewed an email sent to them.

I have tested this and the cache expires pretty quickly. From memory 10min -30. I thought that was fine because its around about one hit per session.

You get enough good information. The IP address would be even better however.

Does Gmail download by default, whether you open the email or not?

Gmail caches by default.

The catch is that Gmail caches all the same images from the same servers, so email marketers get around it by serving tracking pixels with obscure, unique URLs per individual.

Geotargeting fails because it loads on GMail servers.

Yes, I understand the caching part. If Gmail proactively loads/cache the unique pixel before users open the email, then the email reporting is garbage. If they wait for the person to open the email, it is very interesting (even if repeat are not tracked).

I was confused on this, but it looks like the email has to be opened once for Google to cache the image.

How?

     https://jioegijogeijesgioegeg.tracking.example.com/niowefioe.png?sdgsdbuegiu=rojpopwmrmwk

has four places to store unique information.

Does Gooogle's proxy remove all of them?

Download via a proxy and cache the image when you receive the e-mail.

It's processed in the queue and opened. Was it the user? Did it hit Inbox? Where did it got opened? When it's opened? How many times it opened?

All these information's reliability got out of the window with a single optimization. You can't know how this mail was processed and it's fate. So, your tracking pixel and URL returned something useless to you.

Aha so it's not just a proxy. It's a pre-fetching proxy. Understood you.

Edit: oh :(

That’s not how Gmail works and it doesn’t protect your privacy that way:

https://blog.filippo.io/how-the-new-gmail-image-proxy-works-...

That’s not how Gmail works and it doesn’t protect your privacy that way:

https://blog.filippo.io/how-the-new-gmail-image-proxy-works-...

I didn't intend to say or have claimed that Google works this way, but it can be done that way, if one is so inclined.

My mistake. It looks like google still waits for an initial email view to cache the image. Kind of wish they would load images for unviewed emails too.

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