Glossary

Tracking pixel

Related glossary terms

Throttling
Transactional email
Transport Layer Security (TLS)
Triggered emails

Tracking pixel

A tracking pixel is a tiny, invisible 1×1 image embedded in an email, usually hosted on a remote server, that gets loaded when a recipient opens the message. The moment the pixel loads, it sends information back to the sender’s platform, allowing them to track basic engagement metrics. 

Unlike cookies, which store data on a user’s device, tracking pixels operate passively and are harder for users to detect or block (though privacy features like Apple’s Mail Privacy Protection are changing that). 

When the email client permits it, the pixel can reveal: 

  • That the email was opened 
  • Timestamp of the open 
  • IP address and rough location (city/region) 
  • Device or operating system used 
  • Whether images were automatically downloaded 

Some platforms estimate metrics like read duration or forward rates based on behavior around the pixel, but these are not always reliable. 

Tracking pixels are found in email headers or footers, often embedded in a logo or an invisible <img> tag. Marketing automation platforms and ESPs (like Mailgun) use them to power open rate reporting, A/B testing, audience segmentation, and campaign optimization. 

Note: With privacy changes from Apple, Gmail, and others, open rates are increasingly unreliable as a primary performance metric. Many marketers are shifting towards clicks, conversions, and downstream activity as more meaningful indicators of engagement. 

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