Rule 34 is an internet meme stating that for every topic or interest on the planet, there is pornographic content involving it. Rule 34 is a comment on the vast range of adult content available online, including content that is taboo or offbeat.
The meme considers traditional porn and modern online pornographic content including hentai, fan fiction, and slash fiction. Rule 34 is a noun, but it can also form a verb. If someone "Rule 34s" something or someone, they create porn about them.
Some people attribute the Rule 34 meme to webcomic artist Peter Morley-Souter. In 2003, he created a work showing his shock at a Calvin and Hobbes themed pornography. This work had the caption “Rule #34: There is porn of it. No exceptions.” Many modern sources citing the rule now omit the “No exceptions” portion. Morley-Souter stated he heard the term in an IRC chatroom.
In May 2007, a searchable online Rule 34 database, featuring Rule 34 images, launched on Paheal.net. This spawned several similar databases celebrating Rule 34.
That same year, popular webcomic xkcd released the comic “Rule 34.” It referenced the rule and unlikely sexual scenarios, including porn set on storm-chasing vans and porn involving homoerotic spelling bees.
In 2008, 4chan users began posting explicit porn parodies and comics demonstrating Rule 34. People requesting specific Rule 34 porn on the website coined a new term for their requested porn, rule 34, Pr0nz.
By 2009, Rule 34 had entered mainstream culture. The Daily Telegraph ranked Rule 34 number three on its list of top 10 internet rules. In 2011, the concept inspired Charles Stross’s acclaimed science fiction novel, also called “Rule 34.” By 2013, CNN called Rule 34 “likely the most famous” internet rule.