Democrats questioned whether steps taken to flag that President Trump's claims of election fraud were "disputed" had gone far enough.
Republican members of the Judiciary Committee asked whether the tech firms should be taking such action at all.
This was the second time the CEOs had been cross-examined in three weeks.
They were previously questioned by the Senate Commerce Committee last month in what was a more rowdy event.
Once again, the issue of a law known as Section 230 loomed large.
It says the platforms are generally not responsible for illegal or offensive things users post on them.
President-elect Biden has suggested the regulation should be "revoked" since it encourages the spread of falsehoods, and several of the Democratic senators at the latest hearing followed his lead.
Republicans also voiced concern of their own.
They said the social media companies were taking editorial decisions about what to take down, label or leave unaltered.
This, they said, made them publishers rather than just distributors of information, and as a consequence they should not be covered by Section 230 in its current form.
"Federal law gave you the ability to stand up and grow without being hit by lawsuits," said Republican Senator Blackburn.
"You have used this power to run amok."
Republican Senator Lindsey Graham, chairman of the Senate Judiciary Committee, added: "When you have companies that have the power of governments, have more power than traditional media outlets, something has to give."