The Trump administration on Monday abruptly closed down a government program created by the Biden administration to allow migrants to use an app to secure an appointment for admission into the United States through legal ports of entry, signaling the start of President Trump’s promised crackdown at the southern border.

Moments after Mr. Trump took the oath of office, an announcement posted on the CBP One program’s website declared that the app would no longer function and that “existing appointments have been canceled.”

The program, which debuted in early 2023, allowed 1,450 migrants a day to schedule a time to present themselves at a port of entry and seek asylum through U.S. immigration courts. More than 900,000 migrants entered the country using the app from its launch in the beginning of 2023 to the end of 2024.

A former Department of Homeland Security official who spoke on the condition of anonymity said that around 30,000 migrants had appointments to enter the United States through the app as of Monday morning.

At the El Chaparral border crossing in Tijuana, Mexico, dozens of migrants who stared at their phone screens trying to check whether their appointments were still valid instead found the crushing message that they no longer existed.

“I am in shock,” said Maura Hernandez, who received the news on Monday morning as she arrived in Tijuana with her four small children from the state of Michoacán. She had a scheduled appointment on Tuesday.

“I don’t know what is going to happen to us,” she said, adding that they had fled their home amid rampant insecurity.

The program was a key part of the Biden administration’s effort to gain control over migration through the southern border. On the one hand, the administration blocked asylum for migrants who crossed illegally. At the same time, U.S. officials believed that by offering migrants an organized way to enter legally through an app, they could discourage attempts to gain entry without authorization. Border numbers have dropped dramatically in recent months, and officials believe the program is a major reason.

“I would say that the model that we have built of restricting asylum at our southern border and building accessible, lawful, safe and orderly pathways for individuals to seek relief under our laws is the model that should be sustained,” said Department of Homeland Security Secretary Alejandro Mayorkas in an interview with NPR this month. “And we have delivered the border and those accessible pathways to the incoming administration.”

The end of the program will test that theory as the Trump administration moves toward a more restrictive policy at the border. The former homeland security official said that they estimated that, in total, nearly 300,000 migrants were in Mexico waiting to use the app.

“We are so disappointed,” said Gustavo Selva from Venezuela after reading the update on his phone that the program had been shut down. He had received hopeful news of his scheduled appointment 21 days ago.

Two days ago, however, he received an email informing him that it had been delayed until Feb. 9. By then, he had already traveled to Tijuana from the southern state of Chiapas after waiting there for seven months for his appointment to go through.

“We thought we could enter today without a problem,” Mr. Selva added. “Now we will be stranded here indefinitely.”

Critics of the program, especially Republican lawmakers, viewed it as a way to allow those who otherwise had no way of entering the U.S. to come into the country and remain for years as their immigration cases languished in the courts.

“The fact that this application exists is the most underreported scandal of the Biden admin. They made an application to facilitate illegal immigration. It boggles the mind,” Vice President JD Vance said in a social media post last week.

Matthew Hudak, a former senior Border Patrol official, said the decision was a clear sign that things were changing at the southern border.

“Simply wanting to immigrate to the U.S. and signing up to get in line will be replaced by more stringent policies that will significantly raise the bar for those seeking to come here, including reimplementing the Remain in Mexico program,” he said. “Many will be left to decide if they will work through the legal process or attempt to enter the country illegally and face what will likely be much more significant consequences.”

Aline Corpus contributed reporting from Tijuana, Mexico.

Like soccer players taking the field in a giant stadium, the 12 finalists ran through a glowing “hype tunnel,” some wearing jerseys with sponsorship logos. As an announcer bellowed introductions and cameras captured their every move, they approached a neon-lit stage to raucous cheers.

Then the men sat down at desktop computers, opened their Microsoft Excel spreadsheets and began to type.

Excel, a program that does complex math on a human’s behalf, is often associated, rightly, with corporate drudgery. But last month, in a Las Vegas e-sports arena that typically hosts Fortnite and League of Legends tournaments, finance professionals fluent in spreadsheets were treated like minor celebrities as they gathered to solve devilishly complex Excel puzzles in front of an audience of about 400 people, and more watching an ESPN3 livestream.

Organizers call the event the Microsoft Excel World Championship. “Yes, it is a thing,” the official website says.

At stake was a $5,000 prize, a wrestling-style championship belt and the title of world’s best spreadsheeter. But the organizer, Andrew Grigolyunovich, is dreaming bigger. He hopes to turn competitive Excel into a popular e-sport where pros compete for million-dollar prizes and big-league glory.

“Excel was always thought of as a back-office product,” said Mr. Grigolyunovich, a Sudoku champion from Latvia. But in Vegas, “these people who are working, I don’t want to say boring jobs — but, you know, regular jobs — they could become stars.”

If that seems too ambitious, we’d like to introduce you to Erik Oehm, a software developer from San Francisco, who watched the action from the front row.

“This is the Super Bowl for Excel nerds,” Mr. Oehm said. “If Excel is the center of your universe, this is like hanging out with LeBron James and Kobe Bryant.”

The “LeBron James of Excel,” as he was introduced in Vegas, was Diarmuid Early, 39, an Irish financial consultant who lives in New York, who entered the arena in jeans, sandals and a jersey patterned to resemble abdominal muscles. The Kobe Bryant was Andrew Ngai, 37, a soft-spoken actuary from Australia known as the Annihilator, who began the world championship as its reigning three-time champion.

“We’re friends — for now,” Mr. Early joked as they posed for a photo. But his anxiety was palpable.

“I probably take it too seriously,” he said. “I’m very invested in it.”

The format for the finals was a mock-up of World of Warcraft, an online role-playing game. It required the 12 men (this particular nerdfest was mostly a guy thing) to design Excel formulas for tracking 20 avatars and their vital signs. If that sounds unfathomably complicated, it was: The players were handed a seven-page instruction booklet.

To prepare, Mr. Early adjusted the width of his Excel columns with the precision of a point guard lining up a 3-point shot. Mr. Ngai queued up a YouTube compilation of “focus music.”

After an announcer kicked off the 40-minute event — “Five, four, three, two, one, and Excel!” — the 12 players leaned over their keyboards and began plugging in formulas. One example: “=CountChar(Lower(D5),”W”)” allowed one competitor, Michael Jarman, to figure out how many times the letter “W” appeared in a spreadsheet.

The aim was to score as many points as possible while staying ahead of rolling eliminations. As cascading answers filled Excel columns, Mr. Ngai took a significant lead, to audible gasps. Then he got stuck on a problem, as did Mr. Early. Mr. Jarman pulled ahead as the two front-runners frantically tried to troubleshoot.

“Oh my gosh, oh my gosh,” Mr. Oehm chanted.

‘Well, this is ridiculous.’

The first electronic spreadsheet was VisiCalc, an “electronic blackboard” that automated pen-and-paper calculations. Microsoft introduced Excel in 1985. The company says its suite of office software, which includes Excel, has more than 400 million users. (Google has said that more than three billion people use its free suite of products, including Gmail and a spreadsheet program called Sheets.)

Part of the appeal, and the intimidation factor, of spreadsheets is their undefined scope. Excel can be a dating organizer or a tool for collating a country’s coronavirus caseload, for example.

Speaking in almost philosophical terms, Bob Frankston, a founder of VisiCalc, said that people who treat Excel merely as a finance tool ignore its vast potential. “They don’t realize it’s a mirror” of their minds, he said. “The financial planning tool they’re seeing is in their head.”

But for millions of people, it’s still just a tool for accomplishing the tasks their corporate overseers assign to them. It may say something about our times that the instruments of our servitude are also the basis of our games.

The first Excel competition, ModelOff, started in 2012. But ModelOff, which featured financial problems that took hours to solve, was not designed with thrills in mind.

When ModelOff was discontinued after seven years, Mr. Grigolyunovich, a former competitor, created the Financial Modeling World Cup, the organization that runs the Excel championship and other events. The championship — which has several corporate sponsors, including Microsoft — was held in person for the first time last year. He said its shortened rounds, eliminations, commentators and pregame “hype tunnel” were designed to raise tension and lure spectators.

“I remember thinking ‘Well, this is ridiculous, why do we have this?’” Mr. Jarman, 30, a British financial consultant who lives in Toronto, said of the tunnel. “But it’s all in good fun. And if the other e-sports do it, we should too.”

Mr. Grigolyunovich said his vision for future tournaments includes more spectators, bigger sponsors and a million-dollar prize for the winner. For now, many fans find out about the Excel championship through ESPN’s annual obscure sports showcase, where it is sandwiched between competitions like speed chess and the World Dog Surfing Championships.

Reluctant rivals

The competitors in Vegas said winning requires not just Excel-know how, but also problem-solving acumen, composure under pressure and intuition — or luck. Add the frisson of a live audience, they say, and the competition starts to resemble a sport in its unpredictability, if not physicality.

They seemed less interested in Mr. Grigolyunovich’s visions of fame and fortune, and more focused on adjusting to the transformation of their staid, niche hobby into a televised spectacle. Mostly they had come to geek out with fellow Excel buffs. Between rounds, they attended spreadsheeting workshops and added each other on LinkedIn.

More rivalries could help to build some excitement, several contestants said — but they were too polite, and on too friendly terms with one another, to initiate any.

“Basically everything that they do to make it more fun for viewers makes it more traumatic for competitors,” Mr. Early said.

There was a bit of celebrity stardust in the air, though, as Mr. Early and the Mr. Ngai, the LeBron and Kobe of Excel, fielded a stream of selfie requests.

“This guy is amazing,” one quarterfinalist, Joy Hezekiah Andriamalala, a finance student from Madagascar, said to a reporter after snapping a photo with Mr. Ngai. “Do you know him? Personally?”

Mr. Ngai, who appeared resigned to the possibility of losing his championship streak, admitted that being a minor celebrity for a few days was “pretty cool.” He said he had started to treat competitive Excel more like a sport than a hobby, setting aside more time to practice.

Onstage, the front-runners tried to prevent Mr. Jarman from running away with the championship belt. Mr. Early won a semifinal round by turning screens of mazes made of colored cells and emojis into numbers. In the finals, Mr. Ngai tried a Hail Mary: filling his remaining cells with random numbers.

As the clocked ticked down to zero, Mr. Jarman turned to stare at the leaderboard.

“Ten seconds, is anything going to happen?” a commentator, Oz du Soleil, shouted. Nothing did.

Mr. Jarman leaped out of his seat and threw his hands in the air, his face gleaming with sweat. The audience erupted. “Look at that! Look at that!” Mr. du Soleil yelled.

Mr. Jarman held the championship belt aloft as someone dumped glitter on his head. Mr. Oehm let out a breath he had been holding.

“You’d never see this with Google Sheets,” he said. “You’d never get this level of passion.”