Here is a short list of the things that could be collected about you from your web browsing behaviors:
Device and browser data: IP address, screen resolution, browser type, add-ons, bookmarks, fonts, apps, clock drift, hardware details, etc.
Location: Geolocation of IP address. GPS coordinates of the device at any time of day.
Web trackers: Your cursor movements and actions, eye movements recorded through the device camera, audio, session details such as mouse clicks, pages visited, items looked at, viewing duration, etc.
Websites, email and social media: user names, passwords, full name, age, address, telephone number, SS#, DL#, financial records, health records, marital status, sexual preference, educational history, credit history, types of cars you own or have owned, bills you pay, items in your shopping carts, web sites you visit and the frequency, your preferred language, affiliations you belong to, email content, social media feeds, IMs, photos, videos, files downloaded, web searches, and so much more.
We could keep going on but we think you get the picture! As much as you think the websites are providing you free information or service, there is nothing free about it. Like the saying goes “if it’s free, then there has to be a catch.” Oh, and that catch is you and your privacy!