A tracking pixel is a tiny, usually invisible image — often 1x1 transparent — embedded in an email or web page. When the recipient's email client loads the image from the sender's server, that request is recorded as an "open". Tracking pixels are how most email tools measure the open rate.
How a tracking pixel works
The pixel is added as an image tag pointing to a unique URL for that message and recipient. When the email is displayed and images load, the server logs the request — with a timestamp and often device or location data — and counts an open. Because it depends on images loading, a tracking pixel cannot see opens when a recipient blocks images, and it can over-count when a system preloads images. Apple Mail Privacy Protection (MPP) does exactly that, which is why open rates are now less reliable on their own.
Why the tracking pixel matters
Tracking pixels still power open reporting, engagement scoring and send-time insights, but they should be read alongside click data — clicks are recorded by link tracking, not the pixel, and are harder to inflate. Combine both for a fuller picture and pair them with a heatmap and click-through rate. Read how Apple MPP affects open rates, see email opening statistics, or explore open-rate reporting.
Mailpro and analytics
Opens, clicks and heatmaps in real time
Mailpro measures opens, clicks and where readers tap with a live heatmap, so you read engagement from more than one signal — and see it the moment a campaign goes out.