The open-ended ban on political advertising is especially significant, after Facebook resisted calls to remove the ads for months. Last month, the company had said it only would stop accepting new political ads in the week before Election Day, so existing political ads would continue circulating. New political ads could have resumed running after Election Day.
But Facebook lags other social media companies in banning political ads. Jack Dorsey, Twitter’s chief executive, banned all political ads from the service a year ago because, he said, they could rapidly spread misinformation and had “significant ramifications that today’s democratic infrastructure may not be prepared to handle.” Last month, Google said it, too, would ban all political and issue ads after Election Day.
Mr. Zuckerberg has said that ads give less well-known politicians the ability to promote themselves, and that eliminating those ads could hurt their chances at broadening their support base online.
Facebook also said it would rely on a mix of news outlets, including Reuters and The Associated Press, to determine whether a candidate had secured the presidency. Until those news organizations called the race, Facebook said, it would place notifications in the News Feed to say no candidate had won. That buttresses what the company had said it would do last month, when it announced that it would attach labels to posts redirecting users to Reuters if Mr. Trump or his supporters falsely claimed an early victory.
To tamp down on potential intimidation at ballot boxes, Facebook also plans to remove posts that call for people to engage in poll watching “when those calls use militarized language or suggest that the goal is to intimidate, exert control, or display power over election officials or voters.”
Mr. Trump and others have talked about watching polls in recent weeks. In a debate with Mr. Biden last week, Mr. Trump urged his supporters to “go into the polls and watch very carefully” on Election Day. His son, Donald Trump Jr., said he wanted to see an “army for Trump” swarming the polls, raising concerns about the threat of violence at the ballot box.
Facebook, which has been criticized for unevenly removing posts and inconsistently enforcing its policies against toxic content, said it had already taken down many posts where people were trying to interfere with the vote. Between March and September, it removed more than 120,000 posts from Facebook and Instagram in the United States because the messages violated its voter interference policies.