Facebook has recently launched "off facebook activity" which lets you see all the activities shared by other apps/websites that you have interacted with.
But how did those apps and websites share that data with facebook, even when I didn't use facebook to log into them? In some cases, I have just surfed a website as an anonymous user, without signing up. Yet they were able to share activity data with Facebook.
Also please note the activities are NOT shared anonymously, but to my specific Facebook account. How did the website get access to my FB account id even when I didnt use FB to login?
622 Apps have shared data to FB
Although I used FB to login only into 5 apps.
You can access off facebook activities here https://www.facebook.com/off_facebook_activity/