Online advertisements can be tracked using cookies, which are small pieces of data that are stored on a user’s computer by a website they visit. When a user visits a website that displays an advertisement, the website can set a cookie on the user’s computer that contains information about the advertisement, such as the content of the advertisement, the website that displayed the advertisement, and the date and time the advertisement was displayed.

There are also other methods for tracking online advertisements, such as using tracking pixels, which are small transparent images that are embedded in web pages and emails. When a user loads a web page or opens an email that contains a tracking pixel, the pixel sends a request to the server that is hosting it, which allows the server to record information about the user, such as their IP address and the date and time the pixel was viewed.

Online advertising networks and analytics platforms also use various technologies to track and analyze the effectiveness of online advertisements. These technologies can include browser fingerprinting, which involves collecting information about a user’s browser and device to create a unique identifier, and device fingerprinting, which involves collecting information about a user’s device, such as its hardware and software, to create a unique identifier.

Overall, tracking online advertisements can help advertisers understand how well their advertisements are performing, who is seeing their advertisements, and how to optimize their advertisements for better results. However, tracking online advertisements can also raise privacy concerns, as it can allow advertisers to collect and use personal data about users without their knowledge or consent.