European lawmakers are about to vote on legislation that critics say would significantly damage Internet freedom.
According to the new copyright directive, online content platforms such as Google and Facebook should use filtering systems that block content, such as images and videos, that infringe the copyright of the copyright owner.
In addition, publishers of "new media" should pay news organizations for the rights to share articles and other content protected by copyright, something that critics claim is an effective "tax" on links.
This could have a particularly damaging effect on companies like Google, Facebook and Twitter, whose platforms are based on the exchange of news content, images and videos.
Copyright regulation is part of the EU's "digital single market", a strategy aimed at establishing a common standard for online services and businesses.
In protest of the law, Italians and Wikipedia language versions blocked access to users earlier this week, arguing that the law will impose "new barriers, filters and restrictions" that prevent users from sharing content .
Wikimedia, which hosts the popular online encyclopedia, is one of a number of opponents of the law, calling it "a threat to our fundamental right to freely share information."
Mozilla, the signature behind the Internet browser Firefox, also objects, arguing that the law could "filter and block much more routine online content."
And Tim Berners-Lee, the inventor of the World Wide Web, and Jimmy Wales, the founder of Wikipedia, were among a series of high-profile industry figures to jointly sign an open letter last month criticizing the proposed law as an "imminent threat" to the future of the Internet.