Tracking pixel
A tiny, usually invisible image in an HTML email whose unique URL tells the sender's server when, and from where, the message was opened.
What it means
Each recipient's copy gets an image URL with a unique ID, and when the mail program loads the image the request records an open, with its time, IP address and software. SendGrid, for example, adds a transparent one-pixel image to the end of the email for open tracking.
Several things now blunt it. Apple Mail Privacy Protection hides the reader's IP address and prevents senders from seeing whether a message was opened. Gmail checks images before display so senders cannot use them to learn the reader's location or set cookies. Classic Outlook blocks automatic picture downloads by default and names tracking pixels as a reason. SendGrid notes that privacy laws in many countries treat such pixels as tracking that needs the recipient's consent.
Related terms
On this site
Sources
What this definition rests on. The wording is ours; the facts are theirs.
- Twilio SendGrid Docs: Tracking settings (open and click tracking)twilio.com
- Apple Support: Use Mail Privacy Protection on iPhonesupport.apple.com
- Google, Gmail Help: Turn images on or off in Gmailsupport.google.com
- Microsoft Support: Block or unblock automatic picture downloads in classic Outlooksupport.microsoft.com
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