Trump's speech was largely a recycling of the same litany of misinformation and unsubstantiated allegations of voter fraud that he has been making for the past month.

The posts on Twitter, Facebook and other sites are imposing a real-time test of Silicon Valley's much-touted rules on handling election misinformation and premature claims of victory.

Beginning Thursday, U.S. Facebook users who post about voting may start seeing labels directing readers to authoritative information about the upcoming presidential election.