


The first web beacons were small digital image files that were embedded in a web page or email. The image could be as small as a single pixel (a "tracking pixel") and could have the same colour as the background, or be completely transparent. When a user opens the page or email where such an image is embedded, they might not see the image, but their web browser or email reader automatically downloads the image, requiring the user's computer to send a request to the host company's server, where the source image is stored. This request provides identifying information about the computer, allowing the host to keep track of the user.

This basic technique has been developed further so that many types of elements can be used as beacons. Currently, these can include visible elements such as graphics, banners, or buttons, but also non-pictorial HTML elements such as the frame, style, script, input link, embed, object, etc., of an email or web page. 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.
