What information does Facebook get when I visit a site with the Like button or another social plugin?
If you’re logged into Facebook and visit a website with the Like button or another social plugin, your browser sends us information about your visit. Keep in mind that Facebook isn't retrieving this information. Since the Like button is a little piece of Facebook embedded on another website, the browser is sending information about the request to load Facebook content on that page.
We record some of this information for a limited amount of time to help show you a personalized experience on that site and to improve our products. For example, when you go to a website with a Like button, we need to know who you are in order to show you what your Facebook friends have liked on that site. The data we receive includes your user ID, the website you're visiting, the date and time and other browser-related information.
If you’re logged out or don’t have a Facebook account and visit a website with the Like button or another social plugin, your browser sends us a more limited set of information. For example, because you’re not logged into Facebook, you’ll have fewer cookies than someone who's logged in. Like other sites on the internet, we receive information about the web page you're visiting, the date and time and other browser-related information. We record this information for a limited amount of time to help us improve our products. For example, we sometimes find bugs in the systems we’ve built to gather aggregate data on how people are interacting with sites that use the Like button or other social plugins. It’s helpful to be able to reference this anonymized information when investigating these bugs so we can find their sources and fix them quickly.