How Are Emails Detected as “Viewed”?
Overview
Section titled “Overview”Emails are often tracked to determine when a recipient has opened or viewed them. The most common technique used for this purpose is pixel tracking — a small, invisible image embedded in the email that signals when the message is opened.
How It Works
Section titled “How It Works”Embedding a Tracking Pixel
Section titled “Embedding a Tracking Pixel”A tiny, transparent image (typically 1×1 pixel) is inserted into the email body, for example:
<img src="https://yourdomain.com/track/open?id={email_id}" width="1" height="1" style="display:none;" />This image is hosted on a tracking server.
When the Email Is Opened
Section titled “When the Email Is Opened”When the recipient’s email client loads the message and its images, it automatically requests the tracking pixel from your server.
Recording the Event
Section titled “Recording the Event”Each request to the pixel endpoint can be logged with metadata such as:
- Email ID or campaign reference
- Timestamp of open
- IP address and device information (if applicable)
- User agent (browser or email client)
This information is stored to mark the email as “viewed” or “opened.”
Limitations
Section titled “Limitations”Image Blocking
Section titled “Image Blocking”Many email clients block remote images by default, meaning the pixel may not load until the user allows images.
Privacy Restrictions
Section titled “Privacy Restrictions”Regulations like GDPR and CCPA limit the collection of identifiable data without user consent.
Partial Visibility
Section titled “Partial Visibility”If the user previews the email without loading images, it may not register as opened.