What an open pixel is

An open pixel is an image one pixel square, usually invisible, with an address unique to one email and one reader. When the email is displayed, the mail client fetches the image, and the server that sent it learns that the email was opened, when, and often from where and on what device.

It is the most common measurement in email, and it would have been easy to add one to every signature we build. A signature goes out on every email a person sends, so the numbers would have been impressive. We chose not to.

When opens stopped meaning opens

In June 2021 Apple announced Mail Privacy Protection for iOS 15 and macOS Monterey. In Apple's words, it "helps users prevent senders from knowing when they open an email", and it hides the reader's IP address too.

The way it does that matters. With the feature on, Apple Mail loads a message's images through Apple's own servers as the message arrives, whether or not anybody reads it. Postmark, which delivers email for a living, describes the result plainly: the preloading triggers its tracking pixel, and reports an open that never happened. An open rate built on pixels now counts machines as well as people, and there is no way to tell them apart.

In the UK, the Information Commissioner's Office uses a tracking pixel in a marketing email as a worked example in its guidance on storage and access technologies, and says the consent rules for those technologies apply to it. In the European Union, the European Data Protection Board's guidelines on the ePrivacy Directive reach the same conclusion about tracking pixels in email.

A signature goes to everybody a person writes to: clients, strangers, suppliers, friends. None of them signed up for anything, and a signature has no moment in which to ask them. A measurement that needs consent nobody can give is one we should not build.

Why a click says more

An open, even an honest one, says that an email was displayed. A click says that a person read something under your name and chose to act on it: they wanted the viewing, the booking page, the case study. It is the signal a sender actually cares about, and it involves nothing the reader did not choose.

What we count instead

  • Clicks on your signature's links, as a total per link, while link tracking is on.
  • Where a click came from, as a count per country and per phone or computer. No IP address, no browser details, nothing that identifies a person.
  • Banner loads for campaigns, as a number per campaign per day, labelled as rough, because the same preloading that broke opens inflates them too.

Link tracking can be switched off at any time, on the dashboard, and then nothing about clicks is recorded either.

What it costs us

Some people arrive from email marketing tools expecting an open rate, and our dashboard does not have one. Rather than leave a blank where they look for it, the dashboard says why. We think a smaller number that means something beats a bigger one that does not, and we would rather make that case than quietly add a pixel to other people's inboxes.