4chan is an anonymous English-language imageboard website that was launched in October 2003 by Christopher "moot" Poole. The site hosts boards dedicated to a wide variety of topics, from video games and television to literature, cooking, weapons, music, history, anime, fitness, politics, and sports, among others. Users typically post anonymously, and registration is not available. As of 2022, 4chan receives more than 22 million unique monthly visitors, of which approximately half are from the United States.

4chan was created as an unofficial English-language counterpart to the Japanese imageboard Futaba Channel, also known as 2chan, and its first boards were originally used for posting images and discussion related to anime. Following 4chans return, several non-anime related boards were introduced, including /k/ (Weapons), /o/ (Auto), and /v/ (Video Games).

4chan is known for its anonymity and over-18 age limit, which means that it is unsafe for teens to use 4chan, 8chan, and their counterparts. Although the site has rules in place for each board, the most popular board, /b/ or ‘random’, has fewer rules. In fact, it allows hate speech such as racism and transphobia along with specific pornographic and grotesque content.

4chan has been at the center of many controversies in the media and may impact online safety. It has been associated with Anonymous, a worldwide protest against the Church of Scientology held by members of Anonymous. Through its association with Anonymous, 4chan has become associated with Project Chanology.

In summary, 4chan is an anonymous imageboard website that hosts boards dedicated to a wide variety of topics. It is known for its anonymity, over-18 age limit, and controversial content.