Twitter has marked at least a dozen tweets from President Trump since Election Day with a disclaimer warning that they may contain "misleading" information about the vote.
"Some or all of the content shared in this Tweet is disputed," the Twitter notice says.
Trump and many of his supporters have gone on Twitter tirades this week as votes continue to be counted in the battleground states of Georgia, Pennsylvania and North Carolina, and the president's early leads dwindle or vanish.
He and his team have promoted claims that those states are engaging in voter fraud, illegally counting ballots cast after Election Day and refusing to allow poll watchers close enough to observe the proceedings.
Several flagged tweets included video clips of Trump's press conference on Thursday, an address from the White House claiming, without evidence, that Democrats were trying to steal the election from him.
In others, he declared himself the winner, despite votes in at least three states still being counted, and in one, he said, "STOP THE FRAUD!"
Trump slammed Twitter for flagging his posts, calling the platform led by CEO Jack Dorsey "out of control." The president has 88.4 million followers on Twitter, compared with 13.9 million for Biden and 121.5 million for former President Barack Obama.