The "like facebook" button is a feature on social networking site Facebook. It was first launched on February 9, 2009. The like button makes it easy for users to interact with status updates, comments, photos and videos, links shared by friends, and ads. When a user clicks, the specified content will be displayed in the user's friend's news feed, and the button will also display the number of other users who like the content, including a list of all or part of these users. The like button expanded to comments in June 2010. After extensive testing and public doubts about whether it intends to merge the "don't like" button, Facebook officially launched the "response" to global users on February 24, 2016, asking users to press and hold the "like" button to choose to use one of the five predefined emotions, including "love", "ha ha", "wow", "sad" or "angry". In May 2017, the response also expanded to comment.

The like button is one of Facebook's social plug-ins that can be placed on third-party sites. Its use revolves around a form of advertising network in which it collects information about which users visit which websites. This form of functionality, a web beacon, has been heavily criticized for privacy. Privacy activists urged Facebook to stop collecting data through the plug-in, and the government has launched an investigation into possible violations of privacy laws. Facebook said it would anonymously process the information after three months, and the data it collected would not be shared or sold to third parties. In addition, the potential use of the like button to measure popularity has led some companies to sell "like" through fake facebook accounts, which in turn has led to complaints from companies advertising on Facebook, which have received a large number of fake likes, thus distorting the right user metrics. Facebook said in its terms of service agreement that users can only create one personal page, and it has been trying to prevent the spread of fake accounts.