Several top websites, including Wikipedia, will go dark on Wednesday to protest the Stop Online Piracy Act (SOPA) and Protect IP Act (PIPA).
The bills are designed to stop piracy and protect copyright holders, but critics say it would amount to censorship and restrict free speech.
Wikipedia, the sixth most visited website in the world, is the latest site to agree to shut down on Wednesday. Founder Jimmy Wales wrote on Twitter:
"This is going to be wow. I hope Wikipedia will melt phone systems in Washington on Wednesday. Tell everyone you know!"
Other sites going dark include TwitPic, Wordpress, Mozilla, Reddit and Boing Boing.
"If you want an Internet where human rights, free speech and the rule of law are not subordinated to the entertainment industry's profits, I hope you'll join us," said Cory Doctorow of Boing Boing.
Google, Facebook and Twitter support the movement but will not shut down. Google said it will post a link on its homepage to educate people on the issue.
"Like many businesses, entrepreneurs and web users, we oppose these bills because there are smart, targeted ways to shut down foreign rogue websites without asking American companies to censor the Internet," a Google spokesperson told ABC News.