Cookies

A cookie is a small text file that a website creates and stores on your device so the site can keep data about you. It is not a program, virus or malware; it is only a text file.

What cookies do

Cookies let a website recognise your device when you return. They can keep you signed in so you do not have to type your details again, keep items in a shopping basket until your next visit, and store preferences such as a larger text size or dark mode. They also allow personalised content and adverts based on what you did before.

Most cookies hold named-value pairs and a unique ID. A nature club's wildlife-recording site might store patch=woodland, month=May and an ID such as t6wn. The club keeps your list of sightings on its server. When you return, your browser sends the cookie back and the site uses the ID to find your sightings.

First-party and third-party cookies

A first-party cookie is created and used by the same website you are visiting, usually for signing in, baskets and settings. Its scope is limited to that one site, so it is generally low risk.

A third-party cookie comes from a different organisation, such as an advertiser or analytics service, whose code is built into the page. These cookies follow users from site to site so adverts can be matched to them, or count how many visitors view each page.

You can manage or delete cookies in your browser settings. The difference matters because first-party cookies only relate to the one site that set them, while third-party cookies can follow your activity across many sites.