A tracking pixel, also known as a pixel tag or web beacon, is a small piece of code that is placed on a webpage that is designed to track activity on the webpage. When a user visits the webpage, the tracking pixel sends a message back to the server, indicating that the user has accessed the content. This information can then be used to track the effectiveness of an advertisement or marketing campaign and to measure the return on investment (ROI) of the campaign.

Tracking pixels can be used for a variety of purposes, including tracking user activity on a webpage, measuring the effectiveness of an ad campaign, and collecting data for analytics and reporting purposes. They can be used in a variety of contexts, including online advertising and social media marketing.