Email Glossary

Tracking Pixel

A tracking pixel is a 1x1 pixel transparent GIF or PNG image embedded in email HTML. When the recipient opens the email, their mail client loads the image from the tracking server, logging an open event. The pixel typically contains a unique identifier linking the open to a specific recipient.

Limitations of Tracking Pixels

Tracking pixels only work when images are enabled in the email client. Privacy-focused clients like Apple Mail and Gmail block tracking pixels by default, leading to undercounted open rates. Text-only emails and users who disable images are not tracked.

Related Terms

Inbox Placement

Whether delivered emails land in the primary inbox, promotions tab, or spam folder.

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