A man uses cell phone to take a photo of Republican presidential candidate Donald Trump as he speaks at a town hall event in Sandown, New Hampshire.

SAN FRANCISCO — It’s official: President Trump is the single biggest political advertiser on Facebook.

Mr. Trump and his political action committee spent $274,000 on ads on the social network since early May, outpacing the second-biggest spender, Planned Parenthood Federation of America, a nonprofit organization that provides reproductive health care. Planned Parenthood spent just over $188,000 on Facebook ads over the same period.

The ads bought by Mr. Trump and his PAC were also seen the most by Facebook’s users, having been viewed by at least 37 million people since May. That compared with 24 million people who saw the second-most viewed group of political ads, which were also from Planned Parenthood.

These findings were laid out in a new study by a group of researchers from New York University, who used Facebook’s own data to arrive at the results. Facebook in May began an archive of political ads, which is a publicly searchable database that catalogs the ads and identifies which groups or individuals paid for them. Facebook hopes the database will include any ad that has political content and that was aimed at Americans. The researchers conducted their study by scraping all of that raw data.

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Their work provides one of the most comprehensive pictures so far of who is placing political ads on the world’s biggest social network and how much they are spending ahead of the midterm elections in November. Reaching voters through social media has become one of the most effective ways to get a message out, but up until now, the transparency around the practice has been limited. That previously allowed operatives from Russia to target divisive political ads at the American electorate in 2016.

Facebook now requires buyers of political ads on its network to be verified as United States citizens or permanent residents, to cut down on foreign interference. That means Facebook’s political ad archive largely provides a portrait of domestic activity, spotlighting both the digital ad buying of Democratic and Republican elected officials and political candidates, as well as nonprofit organizations, for-profit groups and PACs. The archive also shows how much these ads were actually consumed by the social network’s users.

“One of the challenges in previous election cycles is that we never had a good repository of political ads,” said Daniel Kreiss, an associate professor of communication at the University of North Carolina at Chapel Hill. He said the study was an “important initial analysis that reveals both the potential, and the many limitations, of Facebook’s political ad database.”

The N.Y.U. researchers broke out the top 449 spenders of political ads on Facebook since May for The New York Times. Of those, 210 were left-wing groups, 124 were right-wing groups and 115 groups were politically neutral, they said.

Damon McCoy, conducted the study with two fellow researchers, Laura Edelson and Shikhar Sakhuja, said they were not able to tally the total spending for Republicans and Democrats because their analysis was ongoing, though they planned to release those figures in the future.

As the midterms approach, political consultants have said that Democrats who are running for election are spending a smaller percentage of their ad budgets on digital ads than their rivals, sometimes as little as 10 percent versus more than 40 percent for Republicans. That has spurred volunteer efforts in Silicon Valley, which is widely regarded as liberal, to help bring Democratic campaigns into the digital age.

But the new study found a healthy amount of activity from what the researchers described as left-leaning politicians. Of the top 20 political candidates and PACs purchasing Facebook ads, 12 were identified as Democrats while eight were Republicans, according to data provided by the N.Y.U. researchers.

Facebook’s database worked well for identifying specific ads, Mr. McCoy said, but it did not give an overview of how a particular group or politician was advertising on Facebook. Some groups, he said, used multiple names to promote ads, such as the American Civil Liberties Union, which also had ads placed as the A.C.L.U.

The researchers said they also found 43,575 cases of ads with political content that did not name a sponsor, indicating that whoever purchased the ad did not go through Facebook’s verification process. They added that men and women between the ages of 25 to 34 were the most targeted for ads, while those under 17 or above 65 were the least targeted.

Facebook said it welcomed the new study and hoped others would begin delving into its data.

“This report is the exactly how we hoped the tool would be used — outside experts helping to analyze these ads on Facebook,” said Rob Leathern, Facebook’s director of product management. “It brings more transparency to the messages people see and increases accountability and responsibility over time, not just for us but advertisers as well.”

For Mr. Trump, the new study’s findings confirm previous reports of how active his operation has been on social media. Brad Parscale, the digital ad director for the Trump campaign, has said that his team took advantage of Facebook’s targeted ad campaigns to reach voters in 2016. The group tested highly targeted messages to reach voters across the United States, and then pushed those messages they saw were performing best.

Recent Facebook ads purchased and placed by Mr. Trump’s operation show a similar style of testing, often running a dozen versions of an ad. This week, for example, Mr. Trump’s operation has run dozens of ads on the social network, which seek to rally support to confirm Judge Brett M. Kavanaugh to the vacant spot on the Supreme Court.

The White House did not respond to a request for comment.

The Facebook ads from Planned Parenthood, meanwhile, ran the gamut from those challenging Mr. Trump’s position on reproductive rights to ads about its services in various states.

“Running ads on Facebook is a targeted and cost-effective way to reach both our 2.4 million patients and 12 million supporters,” said Erica Sackin, a spokeswoman for Planned Parenthood. She pointed out that the figures in the database included ads from the organization’s 56 affiliates, including services they provide, as well as “advertisements raising the alarm about what is at risk as the Trump-Pence administration and many states try to take away access to health care.”

“While Facebook is trying to deal with a very real problem of fake news, their solution is far from perfect and creates the unintended consequence of painting a false picture of political advertising on their platform,” Ms. Sackin said.

The only other political candidate to come close to Mr. Trump’s Facebook ad spending was Beto O’Rourke, a Democrat and congressman in Texas’s 16th Congressional district. He put in at least $194,400 since May on Facebook ads that reached roughly 13 million people, according to the researchers. Mr. O’Rourke, who has drawn media coverage for his efforts to challenge Senator Ted Cruz in November, had made Facebook a backbone of his campaign with ads on his local speaking engagements and promoting his grass-roots fund-raising efforts.

According to the study, most other politicians shelled out well under $100,000 on ads on the social network, reaching only hundreds of thousands of Facebook users.

Mr. Beto’s campaign did not respond to a request for comment.