The web is moving away from third-party cookies. Some browsers haven’t supported them for years, in the name of privacy, and even Google is now promising to phase them out in the Chrome browser, eventually.
First, a reminder of what third-party cookies are, because when most of us think of cookies, we tend to think of first-party cookies, which just track our movements on the site that uses them.
Third-party cookies can be accessed by a site other than the one being visited. So for example, with Google Ads, when you visit the Blue Widget Company’s website, Google Ads puts a third-party cookie on your computer to say you’ve been there. Now whenever you visit any site showing Google Ads, the ad server can look up the cookies on your computer, and know that you’ve been to Blue Widget Company’s website – and many others – and what you did on those sites. As advertisers, we love this information, of course; it enables us to show ads to people with a relevant search history.
Google is quite transparent about this: you can see what interests Google has inferred about you here. Give it a try.
Note that you can use this page to turn off ad personalisation entirely, or just exclude personalisation from non-Google activities (under “Advanced”). The latter option only tells Google not to use information gathered on other platforms to show you targeted or personalised ads: the third-party cookies.
Tomorrow I’ll explain what Google is doing to replace this system.