Facebook explains how and why it tracks people who don’t use Facebook

Rob Waugh
Mark Zuckerberg looks glum during Congress grilling (Getty)

Last week, Mark Zuckerberg declined to answer a question from an American Senator on Facebook tracking users when logged out – and in the end suggested that someone else would ‘follow up.’

The social network this week posted a blog explaining how the site and its services track people – even non-users, and people who have logged out.

David Baser, Product Management Director said, ‘When you visit a site or app that uses our services, we receive information even if you’re logged out or don’t have a Facebook account.

‘This is because other apps and sites don’t know who is using Facebook.

The logo of Facebook displayed on a smartphone (Dominic Lipinski/PA)

‘When a website uses one of our services, your browser sends the same kinds of information to Facebook as the website receives. We also get information about which website or app you’re using, which is necessary to know when to provide our tools.’

Baser explains in-depth how Facebook ‘tracks’ users across the web and inside apps – including by the use of ‘hidden’ Facebook Pixels embedded in websites in a post here.


Last week, Senator Roger Wicker asked, ‘There have been reports that Facebook can track user’s browsing activity even after the user has logged off the Facebook platform. Can you confirm whether or not this is true?’

Zuckerberg replied, ‘Senator, I want to make sure that I get this accurate, so it’ll probably be better to have my team follow up with you on this.’

Wicker said, ‘You don’t know this?’

Zuckerberg then replied, ‘I know that people use cookies on the Internet and that you can probably co-relate activities between sessions.

‘We do that for a number of reasons including security and measuring ads to make sure that the ad experiences are most effective, which people can of-course opt out of.

In 2016, Facebook announced that it would track non-users as well as users via its online ad network – using cookies, ‘Like’ buttons and other plug-ins on third-party sites.

If you’re using Facebook, you can switch off some of this functionality.

The option (which you can find by going to the lock icon in Facebook on your PC, then to Settings, then to Ads) says, ‘Your Facebook ad preferences can be used to show you ads on apps and websites off of the Facebook Companies.’

Switching it off will mean that you don’t see ads ‘personalised’ to you on other sites.

The company said its goal is to serve relevant adverts to people who don’t use Facebook – using the data it has on its 1.7 billion users to make inferences about non-users.

This approach is known as ‘lookalike’ targeting.