Cookies are usually small text files stored on a device, such as a personal computer (PC), a mobile device or any other device that can store information. Devices that may use cookies also include so-called ‘Internet of Things’ (IoT) devices that connect to the internet, such as smart TVs.

Cookies can serve a number of important functions, including remembering a user and their previous interactions with a website. They can be used, for example, to keep track of items in an online shopping cart or to authenticate your access to banking services and other online services. They can also be used for online behavioural advertising and for uniquely tracking and profiling website users across their browsing habits and even across their devices and the locations they visit.

Sometimes the term ‘cookies’ is used as a catch-all term for other types of information or technologies that may be stored on a person’s device or terminal equipment or that may be used to track them online. Typical cookies stored on a web browser are ‘http’ cookies. There are other types of storage that may take place on a device, however, such as local shared objects (LSOs), or ‘flash’ cookies. In addition, tracking techniques such as device fingerprinting are also used to gain access to information stored on users’ devices.