The chief executives of Facebook, Twitter, and Google will shortly face questioning by the US Senate over a key legal protection given to their firms.
At present, the firms cannot be sued over what their users post online, or the decisions they make over what to leave up and take down.
But some politicians have raised concerns that this “sweeping immunity” encourages bad behaviour.
The three CEOs will say they need the law to be able to moderate content.
But Facebook’s Mark Zuckerberg will add that he supports changes to the rule “to make sure it’s working”.
Mr Zuckerberg, Twitter’s Jack Dorsey and Google’s Sundar Pichai were summoned before the Senate after both Democrats and Republicans backed a subpoena vote.
Senators are worried about both censorship and the spread of misinformation.
And some industry watchers agree that the legislation – known as Section 230 – needs to be revisited.
“[It] allows digital businesses to let users post things but then not be responsible for the consequences, even when they’re amplifying or dampening that speech,” Prof Fiona Scott Morton, of Yale University, explained to BBC’s Tech Tent podcast.
“That’s very much a publishing kind of function, and newspapers have very different responsibilities. So we have a bit of a loophole that I think is not working well for our society.”
What is Section 230?
Section 230 is the main legal protection for social networks so they don’t get sued.
It means that generally, websites themselves aren’t responsible for illegal or offensive things that users post on them. They’re treated as neutral middlemen – like newspaper sellers, rather than the editors that decide what goes in the paper.
Originally seen as a way to protect internet providers (like BT or Comcast), it’s become the main shield for huge sites like Facebook, Twitter and YouTube, which can’t possibly review every post from their users before they go up.
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But politicians say Section 230 is outdated.
Democrats take issue with the spread of lies online with no consequences for the sites. Republicans argue that big tech is using its moderation powers to censor people it doesn’t agree with – making editorial calls rather than staying neutral.
And both sides agree they want to see the social networks held accountable.
Facebook and Twitter, however, appear to be divided on their strategy ahead of Wednesday’s session.
Twitter boss Mr Dorsey has written to the committee to tell them that “weakening Section 230 protections will remove critical speech from the internet”. He also argues that the law has allowed smaller companies – such as Twitter once was – to compete with established giants without worrying about vast compliance issues.
He also claimed that Twitter itself still “does not have the same breadth of interwoven products or market size as compared to our industry peers”.
Facebook’s Mr Zuckerberg, by contrast, is expected to tell the committee that while Section 230 is “a foundational law” that encourages free expression, he believes that it should be changed “to make sure it’s working as intended”.
“At Facebook, we don’t think tech companies should be making so many decisions about these important issues alone. I believe we need a more active role for governments and regulators,” his prepared remarks say.
But he is expected to also warn senators that any changes should not have “unintended consequences” of stifling innovation or freedom of expression.
Google, which runs YouTube as well as its global search business, did not provide its remarks in advance.
Both President Donald Trump and his election rival Joe Biden have called for the removal of Section 230, though for different reasons.
Mr Trump targeted Twitter with an executive order earlier this year, after it began labelling some of his tweets with warnings.
Mr Biden told the New York Times in January that newspapers “can’t write something you know to be false and be exempt from being sued” – but Mr Zuckerberg could.
With the presidential election looming on 3 November, no outcome will be fully decided before the next presidential term – but the tech giants may face further issues no matter who wins the election.