Why It Matters
Tracking pixels are the foundation of open rate measurement. Without them, you'd have no idea whether anyone read your emails. But they're not perfect. Apple's Mail Privacy Protection (introduced in iOS 15) pre-fetches tracking pixels for all emails, making it look like every Apple Mail user opens every message. This means open rate data from Apple Mail users is now essentially useless — and Apple Mail accounts for roughly 50-60% of email opens.
How It Works
Your ESP inserts a tiny, unique image URL into each email it sends. When a recipient's email client renders the HTML and loads images, it makes an HTTP request for that pixel. Your ESP's server logs the request along with the timestamp, device info, and approximate location. That log entry becomes an "open" in your campaign report. Each recipient gets a unique pixel URL, so the system knows exactly who opened.
Quick Tips
- Don't rely solely on open rates for engagement measurement — click rates are more reliable since Apple's privacy changes.
- Plain-text emails can't contain tracking pixels, so they won't register opens.
- Some corporate email clients block external images by default, which means those opens never get tracked either.
- Use open data as a directional signal, not an exact measurement. The true open rate is always higher than what's reported.