Danbooru is an online imageboard and tag-based image archive using a non-hierarchical structure in which users are able to post content and search for images they want to see through tags and ratings.   The board site was launched in 2005, numerous Danbooru imageboards began to emerged online. 
According to HappyNapping at Urban Dictionary, by 2007 Danbooru had a reputation for hosting child pornography and had already been pressured into banning all furry pictures while allowing images of bestiality.
In 2010, The Internet Sage described Danbooru as having "a very awful community. That includes the admins, mods and janitors."
Role in Gamergate