Recent revelations of harvesting and sale of data by social media platforms have raised concerns about your exposure. This piece cited by Dr. Joseph Mercola shows the kind of data Facebook and Google may have on you:

In a March 30 article for The Guardian, Dylan Curran takes a deep dive into the data harvesting going on between Facebook and Google, and for anyone concerned about their privacy, the results are disconcerting to say the least. Here’s a summary list of the kind of information these two corporations collect, track and store on each and every single user:

Detailed location tracking

If you have a Google-enabled device on your person that has location tracking turned on, it will store the exact details of where you are at any given moment, and this data accumulates from the first day you started using Google on the device. To review the details of your own data, see this Google Maps Timeline link.
Complete search histories on all devices

Google keeps tabs on everything you’ve ever searched for, on any device, including search histories you’ve deleted from an individual device. To check your own search data, see Google’s MyActivity page.
Personalized advertisement profile

Based on your data profile — location, gender, age, work and private interests, relationship status, income, health concerns, future plans and so on — Google creates personalized advertisements that might interest you. Have you ever done a search for a particular product or service and suddenly found yourself flooded with ads for that precise thing? That’s your data profile at work. To see your personalized ad profile, see Google’s Ads Settings.
App usage

Do you use apps and extensions? If so, Google knows which ones you’re using, how often, when, where and with whom you’re interacting when you do. To see your app usage data, check out Google’s Security Permission Settings.

YouTube history

Much can be gleaned from the types of videos you’re interested in, and Google keeps tabs on every single one you’ve ever searched for, watched and commented on. To review your own data, see your Youtube Feed History page.

Facebook interactions

Like Google, Facebook records, tracks and stores every single thing you do on Facebook: Every post, comment, “like,” private message and file ever sent and received, contacts, friends lists, login locations, stickers and more. Even the recurrent use of certain words is noted and can become valuable currency for advertisers.

When Curran downloaded all of the information Facebook has stored on him, he ended up with a 600MG file, or roughly 400,000 word documents. For individuals who start using Facebook at a young age, the lifetime data harvest could be inconceivably large. To view and download your Facebook data, see Facebook’s Download Your Info page.

Webcam access

Your built-in webcam on your phone, tablet, laptop or computer can also be accessed by various apps. To learn more about app permissions, see “How to Master Your App Permissions So You Don’t Get Hacked — The Full Guide,” by Heimdal Security.

As noted in this article, “For a long time, app permissions were something the regular PC user had no idea about. When installing new software on a computer, we were never asked if application X could access our web camera, our list of contacts, etc. … App permissions may seem like a nuisance, but the better you know how they work, the safer you can keep your data.”

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Event tracking

By tracking your Google calendar entries, combined with your location data, Google knows what events you’ve attended, when and for how long.

Your fitness routine

If you use Google Fit, all the details about your fitness routine and workouts, down to how many steps you’ve taken on any given day, are recorded and stored.

A lifetime of photographic evidence

Twenty years ago, photos were a private matter, reminisced over in photo albums and displayed around the home. Today, people’s lives are on public display online, and Google captures it all. When combined with facial recognition software and other technological identification applications, including metadata detailing the time and place of each snap, your photos are a treasure trove of private information.

A lifetime of emails

Google also has every single email you’ve ever sent, received and deleted

Deleted files and information

You probably delete files and information every now and then for the sake of safety, right? You might decide to delete that list of passwords from your phone, for example, in case you lose it or it gets hacked. Well, Google still has all of that information.

As noted by Curran, showing a screen shot of his downloaded Google data, “This is my Google Drive, which includes files I explicitly deleted, including my resume, my monthly budget and all the code, files and websites I’ve ever made, and even my PGP private key, which I deleted, that I use to encrypt emails.”
If you’ve done it or researched it, Google and Facebook have a record of it

Like Facebook, Google allows you to download a copy of the data they have stored on you. Curran’s personal data cache from Google was 5.5GB big, equal to about 3 million word documents. Essentially, your Google account contains a detailed diary of everything you’ve ever done or planned to do, and where you were when you did it. To download your own Google cache, see Google’s Takeout page.
How Is Your Personal Information Being Used?

Google has “your bookmarks, emails, contacts, your Google Drive files … your YouTube videos, the photos you’ve taken on your phone, the businesses you’ve bought from, the products you’ve bought through Google … data from your calendar, your Google Hangout sessions, your location history, the music you listen to, the Google books you’ve purchased, the Google groups you’re in, the websites you’ve created, the phones you’ve owned, the pages you’ve shared, how many steps you walk in a day,” Curran writes, noting his own data cache included:

“… every Google Ad I’ve ever viewed or clicked on, every app I’ve ever launched or used and when I did it, every website I’ve ever visited and what time I did it at, and every app I’ve ever installed or searched for.
They also have every image I’ve ever searched for and saved, every location I’ve ever searched for or clicked on, every news article I’ve ever searched for or read, and every single Google search I’ve made since 2009. And then finally, every YouTube video I’ve ever searched for or viewed, since 2008.