Facebook will also soon start clearly labeling political ads and providing more information about them, like who paid for them.
Facebook is under increasing pressure to crack down on misinformation before this fall’s hotly contested midterm elections. And scrutiny of social media has become even more intense since the Justice Department charged 13 Russians and three companies in a February indictment that revealed a sophisticated network designed to subvert the 2016 election and to support the Trump campaign.
Facebook recently removed 270 accounts associated with Russia’s Internet Research Agency, the “troll factory” that spread misinformation before and after the 2016 election.
“These steps by themselves won’t stop all people trying to game the system,” Mr. Zuckerberg said in his post. “But they will make it a lot harder for anyone to do what the Russians did during the 2016 election and use fake accounts and pages to run ads.”
The new policy for Facebook and for Instagram, which Facebook owns, covers only a part of what appears on those social media outlets. Most regular pages and accounts will still not require verification.
Many of the deliberately misleading or outright false news stories on Facebook are shared among regular users, and they often come from residents of the United States. The company generally doesn’t regulate the content of posts, including their veracity, unless they violate its “community standards,” which prohibit bullying, pornography and threats, among other things.
Facebook’s algorithms also tend to magnify the visibility of sensationalist posts because they tend to draw more clicks, reactions and comments.
Effective immediately, people who want to run Facebook ads regarding political candidates or issues in the United States need to submit proof of a government-issued identification. They also have to have a mailing address in the United States, though some people think it would be easy for foreign agents to set up one.
Facebook will mail a unique code for the advertiser to enter for verification, Andy Stone, a spokesman for Facebook, said. “Advertisers will also have to disclose what candidate, organization or business they represent,” he said in an email.
The program will be rolled out to the rest of the world in the coming months, the company said.
“We’re committed to getting this done in time for the critical months before the 2018 elections,” Mr. Zuckerberg said in his post.
Initially, Mr. Zuckerberg scoffed at the idea that misinformation on Facebook could have played a role in the outcome of the 2016 presidential election. But starting last fall, the company was faced with — and eventually acknowledged — a series of revelations that Russian agents bought ads or spread misinformation on its social media outlets.
Facebook said that between 2015 and 2017, 11.4 million Americans saw ads from the Internet Research Agency and more than 126 million users were likely to have seen the unpaid posts from the group’s Facebook pages.
Law enforcement officials say Russian agents, looking to stir discord, posed as Americans with Facebook pages that represented a range of political viewpoints, from “Blacktivist” to “Heart of Texas.”
The misinformation issue affected many of the company’s more than two billion users around the world. Just a day before Facebook announced its ad changes, civil society groups in Myanmar criticized Mr. Zuckerberg, arguing that he had mischaracterized his company’s effectiveness at detecting and quashing messages encouraging violence in the country.
Facebook’s acknowledgment of its problems has accelerated in recent weeks, after revelations that the political consulting firm Cambridge Analytica, which worked with the Trump campaign, had improperly harvested the data of up to 87 million Facebook users.
Mr. Zuckerberg is set to testify before the Senate’s Commerce and Judiciary Committees on Tuesday and the House Energy and Commerce Committee on Wednesday.
He and Facebook’s chief operating officer, Sheryl Sandberg, have gone on a charm offensive ahead of the hearings. Mr. Zuckerberg spent an hour taking questions from reporters on Wednesday, and Ms. Sandberg has sat for a series of broadcast interviews this week. Both executives signaled that they knew the company had a problem that would not be easily fixed.
Mr. Zuckerberg said Facebook would hire more people for the verifications, but did not say how many. Rob Goldman, Facebook’s vice president of advertising, and Alex Himel, its vice president of local business, said in a separate post that the company would also rely on software “to help find advertisers that should have gone through the authorizations process but did not.”
They added that Facebook was also hoping its users would report political ads that didn’t have proper disclosures.
Facebook will also begin adding “political ad” labels to such posts and will allow users to see who was behind political ads, the basic demographic information about who saw those ads and other ads run by those people, Mr. Goldman and Mr. Himel said. Facebook began testing its verifications over the past several days, “and people will begin seeing the label and additional information in the U.S. later this spring,” they said.
Testing of the political ad disclosures has already begun in Canada and will roll out globally this summer, the company said.
The policy builds on an announcement in October that Facebook would start verifying advertisers running “election-related” ads. Critics said that would not capture many of the ads run by Russian agents around the 2016 election, which focused on issues rather than specific elections. One Internet Research Agency ad, for example, featured a Confederate flag and said, “The South will rise again!”
Facebook’s move on Friday would address those issue ads. Most of the Russian ads focused on “divisive political issues like guns, L.G.B.T. rights, immigration and racial issues,” Senator Mark Warner, Democrat of Virginia, said in a statement.
“That’s why today’s announcement by Facebook is so important,” he added.
Facebook hadn’t always been on board with such disclosures. In October, Mr. Warner co-sponsored the Honest Ads Act, which would require tech companies to disclose who is behind political ads on their sites. Facebook told congressional aides that it would struggle to comply with the legislation because it often struggled to understand whether an ad was political or commercial, and that the sheer number of Facebook ads also complicated that task.
Rachel Cohen, a spokeswoman for Mr. Warner, said on Friday that his office had met with Facebook officials regarding the bill several times and that they hadn’t supported it.
Another co-sponsor of the bill, Senator Amy Klobuchar, Democrat of Minnesota, applauded Facebook on Friday for voluntarily complying with the bill’s proposals, but added in a statement that “a patchwork of voluntary measures from tech companies isn’t going to cut it.”
Facebook’s political-ad disclosures would in some ways do more than what is expected of television networks because the company would allow users to see all of the ads run by a group, said Travis Ridout, a Washington State University professor and co-director of the Wesleyan Media Project, which tracks political advertising.
Still, Facebook’s verification plans don’t seem foolproof, Mr. Ridout said. “It’s certainly a great step to take and helps to solve the problem of foreign influence,” he said. “But I would not be surprised if people get creative and find ways around those requirements.”