Does Facebook receive cookie information when I visit a site with the Like button or another social plugin?
If you’ve previously received a cookie from Facebook because you either have an account or have visited facebook.com, your browser sends us information about this cookie when you visit a site with the “Like” button or another social plugin. We use this cookie information to help show you a personalized experience on that site as well as Facebook, to help maintain and improve our service, and to protect both you and Facebook from malicious activity. We delete or anonymize it within 90 days, and we do not sell it to advertisers or share it without your permission.
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