Quick answer
A tracking pixel, or web beacon, is a tiny, usually invisible image or script embedded in a web page or email. When it loads, the browser or mail client requests it from a server, which records that the page or email was viewed, plus details such as time, IP address and user agent.
What is a tracking pixel?
A tracking pixel (or web beacon) is a tiny, invisible image or snippet placed in a web page or email. When it loads, the browser or mail client fetches it from a tracking server, and that request is the measurement:
<img src="https://ads.example.net/px?event=purchase&value=128.50" width="1" height="1" alt="">The server logs the time, IP address, user agent and whatever is in the URL, and often reads or sets a cookie so it can recognise the browser later.
Three kinds you will meet
| Kind | Placed on | Records | Main limits |
|---|---|---|---|
| Ad conversion pixel | Thank-you or checkout page | That an ad visitor converted | Ad blockers, third-party cookie blocking |
| Email open pixel | Inside an email | That the email was opened | Mail apps preload or block images |
| Analytics beacon | Every page | Pageviews and events | Blockers; depends on what it stores |
Why email opens are no longer reliable
Since 2021, Apple Mail Privacy Protection downloads remote images for many messages in the background, whether or not the person reads them. Every such email looks "opened". Other clients block images by default. Treat open rate as a rough signal and judge campaigns by clicks and conversions.
Privacy checklist
- List every pixel on your site and what it sends.
- Keep personal data out of pixel URLs: no emails or names in parameters.
- Load non-essential ad pixels only after consent where required.
- Remove pixels from campaigns that have ended.
Alternatives
Server-side events send conversions from your server, so they survive blockers and you control exactly what is shared. TapCub's website script writes no cookie and no local storage; conversions can also be sent from your server with the server track API. See cookieless analytics and click IDs.
Related: email campaign tracking.
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Solutions Engineer
Covers SDKs, API integrations, and data implementation, with an emphasis on validation, system interoperability, and troubleshooting.