Logged-in visits to a site with the Like button send Facebook information about the visit
This help article explains what Facebook receives when you visit another website that carries the Like button. If you are logged into Facebook when you visit such a site, your browser sends Facebook information about your visit. The article explains the mechanism: the Like button is a small piece of Facebook embedded on the other website, so loading that page makes your browser request Facebook content, and that request carries information about the visit. The specific items Facebook says it receives in this logged-in case are listed in a separate card (user ID, the website, date and time, other browser-related information), and the stated purposes are in another card. A different, more limited rule applies when you are logged out or have no Facebook account.
Supporting quotations
Information Facebook receives when you visit a site with the Like button
If you’re logged into Facebook and visit a website with the Like button, your browser sends us information about your visit.
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.
Qualifications & exceptions
The article names only the Like button for the logged-in case; the logged-out paragraph speaks of "the Like button or another social plugin".
This is a Help Centre article, not the Privacy Policy; the article itself points to the Privacy Policy for cookie and ad use.
Not stated here
The article does not say whether the same logged-in transmission applies to other social plugins besides the Like button.
The exact contents of "information about your visit" beyond the items the article lists are not stated.
Data Access & Collection · Company practice
When you are logged in, the data Facebook receives includes your user ID, the website, date and time and browser info
For a logged-in visit to a site with the Like button, the article lists what the received data includes: your user ID, the website you are visiting, the date and time, and other browser-related information. The word "includes" presents this as a list of examples rather than a closed list. "Other browser-related information" is not itemized in this article.
Supporting quotations
The data we receive includes your user ID, the website you're visiting, the date and time and other browser-related information.
Qualifications & exceptions
"Includes" is not stated as exhaustive.
Not stated here
What "other browser-related information" covers is not stated in this article.
Whether any of this data is retained, and for how long, is not stated here.
Data Access & Collection · Company practice
Logged-out visitors and people without a Facebook account send a more limited set of information
If you are logged out of Facebook, or have no Facebook account, and you visit a website with the Like button or another social plugin, your browser sends Facebook a more limited set of information than a logged-in visit does. The article explains that because you are not logged in you will have fewer cookies than a logged-in person. It says that, like other sites on the Internet, Facebook receives information about the web page you are visiting, the date and time, and other browser-related information, and that it records this to help improve its products. Unlike the logged-in paragraph, this paragraph does not list a user ID and states only product improvement as the purpose, not personalization. The later ads paragraph speaks of "the information we receive when you visit a site with social plugins" without limiting it to logged-in users, so it is not clear from this article whether logged-out visit information is also used for ads.
Supporting quotations
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 to help us improve our products.
Qualifications & exceptions
Fewer cookies is given as the reason the information is more limited; the article does not say the logged-out set contains no identifier.
The phrase "Like other sites on the Internet" frames this as ordinary web-server information.
Not stated here
Whether the logged-out information is used for ads is not stated in this paragraph; the ads paragraph is not limited to logged-in users.
Which cookies, if any, a logged-out visitor still has is not stated.
Cross-references
qualifies (model-proposed): Logged-in visits to a site with the Like button send Facebook information about the visit — qualifies: The logged-in transmission rule applies only while you are logged into Facebook; when you are logged out or have no account, the article says your browser sends a more limited set of information and states only product improvement as the purpose.