Back to Glossary
Metrics & Analytics

Tracking Pixel

A tiny invisible image that loads when an email is opened, allowing senders to track email opens.

Definition

A tracking pixel is a tiny (typically 1x1 pixel) transparent image embedded in emails to track when they are opened. When the email is viewed and images load, the pixel is requested from a server, which logs the open with details like time and location. This is the primary method for email open tracking.

Why It Matters

Tracking pixels enable open rate measurement, a fundamental email metric. They help you understand engagement, optimize send times, and trigger automations based on opens. However, accuracy is limited by image blocking and privacy features like Apple's Mail Privacy Protection.

How It Works

A unique image URL is embedded in each email. When the recipient opens and images load, their email client requests the pixel from the tracking server. The server logs the request and returns a transparent image. Each request can include unique identifiers to attribute opens to specific recipients.

Best Practices

  • 1Use opens as one signal among many, not the sole metric
  • 2Account for MPP inflation in analysis
  • 3Complement with click tracking for more reliable engagement data
  • 4Consider privacy implications and be transparent
  • 5Do not over-rely on open data for critical decisions

Frequently Asked Questions

Imperfect. Image blocking prevents tracking. Apple's Mail Privacy Protection pre-fetches pixels, inflating open rates. Some opens are bots. Use tracking pixel data directionally, not as absolute truth. Clicks are more reliable.

It is industry standard and generally accepted when disclosed in privacy policies. Be transparent about tracking practices. Respect privacy preferences. The industry is moving toward more privacy-conscious approaches.