What type of data does Facebook collect when I’m not using it?

It is a hard question to answer but I saw the video of Mark Zuckerberg testifying in front of the US Congress where he answered this question. Actually, many websites and apps use Facebook services to make their content and ads more engaging and relevant. These services are like social plugins such as our Like and Share buttons, direct Facebook login,which lets you use your Facebook account to log into another website or app.

When you visit a site or app that uses Facebook services, they receive your information even "if you’re not using Facebook or don’t have a Facebook account''. This is because other apps and sites don’t know who is using Facebook.

When you are not using Facebook and visit a website, your browser (for example Chrome, Safari or Firefox) sends a request to the server of Facebook. The browser shares your IP address so the website knows where on the internet to send the site content. The website also gets information about the browser and operating system (for example Android or Windows) you’re using because not all browsers and devices support the same features. Your browser also shares cookies which can help recognize details like unique visitors, demographic information, and whether the visitor uses Facebook.

Also read:- Does Facebook see sent messages on Whatsapp?