Facebook knows what millions of people do on their phones, even if they don’t actually use the social network, a new report claims.

The company is claimed to have been using data gathered from another firm for detailed insights on people’s app and website usage habits, such as which apps they use, how frequently they use them and even how long they use them for.

This information has also been used to shape Facebook’s product roadmap, and led to it buying WhatsApp and continuing to rip Snapchat’s Stories feature.