Web beacon

This request provides identifying information about the computer, allowing the host to keep track of the user.

The identifying information provided by the user's computer typically includes its IP address, the time the request was made, the type of web browser or email reader that made the request, and the existence of cookies previously sent by the host server.

The host server can store all of this information, and associate it with a session identifier or tracking token that uniquely marks the interaction.

But the company could use web beacons requesting data from its one image server to count and recognize individual users who visit different websites.

"Return-receipt-to" (RRT) email headers can also trigger sending of information and these may be seen as another form of a web beacon.

Using this system, they can send similar emails to a large number of addresses and then check which ones are valid.

[10] It is a standardized API that directs the web client to silently send tracking data back to the server, i.e. without alerting the user and thus disturbing their experience.

[citation needed] Use of this Beacon API enables user tracking and profiling without the end-user's awareness, as it is invisible to them, and without delaying or otherwise interfering with navigation within or away from the site.