Facebook has launched a new tool that lets people see which apps, businesses and websites are sharing their information with the social network.
Many companies track what people do online and share that information with Facebook, to target adverts at them.
The new tool lets people "clear" this "off-Facebook activity" data from their account and opt out of the information being used for targeted advertising.
However, the data will not be permanently deleted.
How does off-Facebook activity tracking work?
When a person is browsing the internet, apps and websites can capture information about them.
This can be something the person provides, such as their email address when they set up an account.
It can also be information scooped up in the background, such as the unique ID of their web browser.
Advertisers can create lists of people they know might be interested in their products and share them with Facebook.
The social network then tries to find Facebook profiles that match information on the list, to show targeted ads.
Off-Facebook activity tracking does not just work online.
Supermarkets, for example, can track purchases via a loyalty card and share this information with Facebook.
Facebook says it is able to offer its platform for free because of the money it earns from advertising.
But it has faced increased scrutiny over the way companies can advertise on the platform, following the Cambridge Analytica data scandal.
The company offers a tool called the Facebook Pixel, which companies can hide on their website.
It tracks who has visited the website and can be used to target advertising.
In 2018, Mark Zuckerberg promised to implement a "clear history" tool for off-Facebook activity.
But while the new tool disconnects a person's profile from the data shared by advertisers, it is not completely deleted.
The tool also lets people opt out of targeted advertising based on off-Facebook activity.
People who opt out will still see ads but they will be "less personalised".
Off-Facebook activity can be tracked in the latest version of the app or on the Facebook website.