Online encyclopaedia Wikipedia will black out its website on Wednesday to protest at anti-piracy legislation under consideration in the US Congress, founder Jimmy Wales said.
Wikipedia will shut down its English versions for 24 hours in protest at the controversial Stop Online Piracy Act and the Protect Intellectual Property Act.
The legislation is designed to crack down on sales of pirated US products overseas. Critics say it could hurt the technology industry and infringes on free speech rights.
Wikipedia is not the first website to announce plans to shut down but is the most well-known, with an estimated 25 million visitors a day.
Reddit, Boing Boing and other online sites also have plans to go dark.
Mr Wales announced the move on Twitter.