The English page of Wikipedia, the world's free online encyclopedia, was dark on Wednesday except for a paragraph urging users to protest legislation designed to stop copyright piracy, but that Wikipedia says "could fatally damage the free and open Internet."
Google's home search page has the logo: "Tell Congress: Please don't censor the web!"
Smaller sites, such as Reddit.com and BoingBoing.net, were also dark, with BoingBoing noting that the proposed anti-piracy bills "would put us in legal jeopardy if we linked to a site anywhere online that had links to copyright infringement."
Some are calling it the largest online protest ever.It's been caused by two bills called better known by their catchy acronyms Sopa and Pipa, which expand to Stop Online Piracy Act and Protect IP Act respectively.
Together, the bills propose to help law enforcers in US reach online piracy originating beyond its shores - to shut down and seize any website peddling counterfeit goods.
News Corp boss Rupert Murdoch is among the supporters of the bills. He tweeted Tuesday: "Don't care about people not buying movies, programs or newspapers, just stealing them."
Though opposed to the bills, big tech names including Facebook and Twitter stayed out of the protests.
The bills have bipartisan support in congress -- both Democrats and Republicans support it -- and is likely to be passed. But they might not make it past the White House.
"While we believe that online piracy by foreign websites is a serious problem that requires a serious legislative response, we will not support legislation that reduces freedom of expression, increases cybersecurity risk, or undermines the dynamic, innovative global Internet," said Obama administration's Victoria Espinel, Aneesh Chopra, and Howard Schmidt in a blog jointly authored by them. This is not an easily settled issue.
Former Senator Chris Dodd, who now chairs the Motion Picture Association of America, labeled the blackout a "gimmick" and called for its supporters to "stop the hyperbole and PR stunts and engage in meaningful efforts to combat piracy."
(With Reuters inputs)