After former President Donald J. Trump was kicked off Twitter in 2021, conservative entrepreneurs rushed to promote social media alternatives tailored to him and his supporters.

There were Parler and Gab, Twitter-like sites popular among the people who stormed the U.S. Capitol on Jan. 6. Then came Gettr, a social media app created by one of Mr. Trump’s former advisers.

That crowded field has now narrowed, giving an edge to Truth Social, the platform that Mr. Trump’s company owns and where he is the main attraction.

In March, Truth Social recorded 1.5 million unique visitors in the United States as its parent company started trading on the public markets, up 130 percent from the previous month, according to Similarweb, a data firm that tracks web traffic. While the app’s visitor count was minuscule compared with mainstream social sites, it was 13 times the size of the combined total recorded by Parler and Gettr.

Truth Social’s closest competitor was Gab, a hotbed for antisemitic and racist posts, which drew 246,000 unique visitors in March, according to Similarweb. (Andrew Torba, Gab’s founder, disputed that figure, saying Gab had about 6.5 million unique visitors in March, but his numbers couldn’t be independently verified.)

Truth Social’s performance has major implications for Mr. Trump’s finances. When the app’s parent company, Trump Media & Technology Group, started trading on the Nasdaq last month, it surged to an $8 billion valuation. Mr. Trump, who owns roughly 58 percent of the company, was suddenly billions of dollars richer, giving him a financial lifeline as he faces hundreds of millions of dollars in legal bills tied to the civil and criminal cases against him.

But just because Truth Social is more popular than some of its competitors doesn’t mean it has a viable business.

Since March, Trump Media’s share price has plummeted, reducing Mr. Trump’s stake to about $2 billion. In securities filings this month, the company revealed that its 2023 revenue was $4.1 million, all of it from advertising, with $58 million in losses.

Truth Social has outpaced the competition mostly because its rivals have faltered. Gettr was plunged into uncertainty last year when a key investor was arrested on fraud charges. Gab isn’t available on mainstream app stores, which banned it in 2017 for allowing hate speech. And Parler is trying to mount a comeback, after it temporarily shut down a year ago amid an ownership reshuffle.

Truth Social is “the best of several unpopular or very niche platforms,” said Josephine Lukito, a social media expert at the University of Texas at Austin who has studied Truth Social. “Even with Donald Trump, it doesn’t have the level of popularity that a mainstream platform has.”

Truth Social remains far behind X, formerly known as Twitter, which has lifted restrictions on fringe political voices since Elon Musk bought it in 2022. X had nearly 115 million unique visitors in March, more than 75 times the traffic on Mr. Trump’s platform, according to Similarweb.

In a statement, Shannon Devine, a Trump Media spokeswoman, said Truth Social had a highly engaged audience of “millions of users,” with thousands of new ones joining every day. She said the company had more than $200 million in the bank and no debt.

Trump Media hasn’t revealed much about the level of activity on Truth Social. In corporate filings, the company omitted data that social media companies typically track closely, like the number of monthly or daily active users. The company hasn’t “relied on any particular key performance metric to make business or operating decisions” as such statistics promote “short-term decision making,” one filing said.

Still, Truth Social enjoys one crucial advantage over other right-wing apps: Mr. Trump.

After Twitter barred him for posts that incited violence on Jan. 6, 2021, Mr. Trump was approached by two former contestants from his reality TV show, “The Apprentice.” They offered to put him at the center of a new platform that wouldn’t censor his posts. Mr. Trump agreed to a deal with Truth Social that gave him a majority stake in the company.

But Truth Social wasn’t the only platform that wanted to build an audience around Mr. Trump. In July 2021, Jason Miller, one of Mr. Trump’s former campaign advisers, launched Gettr, which also had a Twitter-like format.

The competition was fierce. Gettr executives tracked Truth Social’s progress closely, and Mr. Miller once expressed concern that the app had launched a direct-messaging capability before Gettr did, two former employees said.

But Mr. Miller’s primary focus was persuading Mr. Trump to use the site. On TV, he said he had set aside a Gettr handle for the former president.

The charm offensive worried Truth Social’s executives, according to documents that a former employee provided to The New York Times. A daily log that the site’s leaders maintained includes multiple entries mentioning Mr. Miller’s efforts to lure Mr. Trump. (One entry also noted that “Melania really likes the name Truth Social.”)

In 2021, lawyers for Trump Media sent Mr. Miller a cease-and-desist letter, asking him “to cease recruiting President Trump” and citing Mr. Trump’s contract with Truth Social, according to a filing.

Mr. Trump stuck with Truth Social, and Gettr withered. In February 2023, Mr. Miller left the company to join Mr. Trump’s presidential campaign. A month later, federal prosecutors charged one of Gettr’s top investors, Guo Wengui, with money laundering and fraud stemming from a range of his business pursuits.

Mr. Miller declined to comment. Gettr didn’t respond to requests for comment.

Parler also tried — and failed — to get Mr. Trump to post on its site. After the Jan. 6 riot, Apple, Google and Amazon removed the app from their stores, citing issues with content moderation. In 2022, Kanye West agreed to buy Parler, but the deal fell apart, and the site shut down last year.

Parler is scheduled to relaunch next month, said Elise Pierotti, the company’s chief marketing officer. At the moment, the app is in a testing phase and not intended to draw heavy traffic, she said.

As for Mr. Trump, Ms. Pierotti said, “If he’s interested in our platform and wants to hop on, we would be open and love that.”

For now, Gab remains Truth Social’s closest competitor. But the platform, founded in 2016, has faced problems for years. In 2017, Google and Apple removed it from their app stores, citing the proliferation of hate speech.

Gab’s average monthly traffic declined nearly 40 percent from 2022 to 2023, according to Similarweb. In an email, Gab’s Mr. Torba said those numbers were incorrect because Similarweb relies on data from third-party analytics providers that his app doesn’t use. Tom Liu, a vice president at Similarweb, said that the firm also worked with internet service providers to gather data, and that it applied a common methodology across the websites it evaluated.

Before Trump Media’s public debut last month, there were signs that Truth Social’s growth was stagnating. The site drew about 100,000 new users in the six months before the public offering, according to estimates by the Stanford Internet Observatory, compared with nearly 250,000 users in the same period a year earlier. But in March, the site’s user count spiked by more than 100,000.

As part of a public company, Truth Social has other advantages, including publicly traded shares that it could use to make acquisitions or ramp up hiring. On Tuesday, Trump Media said it was close to starting a video streaming service that would focus partly on “content that has been canceled.”

The platform has also outperformed rivals in attracting other conservative candidates, Dr. Lukito said. Before the 2022 midterm elections, 54 Republican candidates posted on Truth Social, her research shows, compared with 37 on Gettr.

Those figures remained tiny compared with X, which featured posts from 363 Republican candidates.