4Chan is a haven for netizens to anonymously post photos and videos, and to comment on other users' posts.
Set up in 2003, the image-based bulletin board was meant to attract fans of Japanese comics with different boards dedicated to Japanese anime, manga and culture as well as video games, music and photography.
The site has since expanded and has been linked to Internet subcultures and activism, reported the Daily Mirror.
It has a main board titled Random that has few rules governing what can be posted, and is often where controversial photos and videos are uploaded to.
Users also need not register an account to post.
The site has been linked to various high-profile hacks such as in 2008 when former Alaska governor Sarah Palin's e-mail account was broken into by an anonymous hacker, who then posted snaps of the content on Wikileaks, reported the Mirror.