Wikipedia will shut down for 24 hours from 4pm EST today, as part of a protest against a US anti-piracy bill which is already losing support among politicians.
SOPA - the Stop Online Piracy Act - and its sibling the Protect IP Act (PIPA) have angered internet firms and users with plans to shut down access to foreign websites for alleged copyright infringements via DNS blocking, and to stop search engines from linking to them or payment systems from transferring money.
Critics have complained the bills are being pushed through by music and film lobbyists, with big web firms publicly slamming the proposed legislation.
Alongside other major sites, Wikipedia has said it will protest SOPA by turning off the English version of its site tomorrow.
"This will be the first time the English Wikipedia has ever staged a public protest of this nature, and it’s a decision that wasn’t lightly made," said Sue Gardner, Wikimedia Foundation executive director, in a statement on the site.
"In making this decision, Wikipedians will be criticised for seeming to abandon neutrality to take a political position," she said. "That’s a real, legitimate issue. We want people to trust Wikipedia, not worry that it is trying to propagandise them. But although Wikipedia’s articles are neutral, its existence is not."
She said the protest would go ahead despite US politicians seemingly pulling back from SOPA, following the White House making it clear yesterday it did not support the proposed legislation in its current form.
"The reality is that we don’t think SOPA is going away, and PIPA is still quite active," she said.
"All around the world, we're seeing the development of legislation intended to fight online piracy, and regulate the internet in other ways, that hurt online freedoms," she added. "Our concern extends beyond SOPA and PIPA: they are just part of the problem. We want the internet to remain free and open, everywhere, for everyone."
While the protest was backed by sites such as Reddit and BoingBoing, Twitter's CEO Dick Costolo said it would be "foolish" for his own site to join the protest.
“That’s just silly," he said via a message on Twitter, in response to a question asking whether the site would also close down for the day. "Closing a global business in reaction to single-issue national politics is foolish.”
However, he later added that Twitter was "very active on this and will continue to be".