Sean Harding, who spent almost $1.4 million on Whatnot, at home last month.

Sean Harding downloaded Whatnot, a live-shopping app, after rekindling his childhood baseball-card collecting hobby.

Within four months, the 45-year-old accountant had spent almost $1.4 million—from his savings, personal loans, money borrowed from a friend and finally from his employer’s company credit card. When his wife discovered the full tally, she filed for divorce.

“I just kept telling myself one more time, then I’d sell it all and make all my money back,” Harding said. “But it was so easy to just swipe right. You don’t even remember how many times you’ve done it.”

Seven-year-old Whatnot is one of the fastest-growing shopping platforms in America. It allows people to bid, around the clock, on trading cards, squishy toys, designer fashion and instant ramen, auctioned live in high-energy shows within the app.

It has tapped into the addictive qualities of social media, with opportunities fed to you in an algorithm-controlled scroll. Often, users don’t search for a particular item, but instead hope to hit on something by being on the app at the right time.

The design supercharges traditional shopping sites such as eBay and Amazon with high-pressure countdown auctions, often run by hosts who urge buyers to bid higher and faster. The most feverish shows are built around “breaks,” where a person buys an opportunity to win an unknown, potentially valuable, collectible. All the while, emotionally charged chat feeds can amp up the competition.

Little slows down a decision to spend, which comes with one swipe and no additional confirmation or checkout screen.

Whatnot doesn’t disclose total users but said it added 20 million new accounts in 2025. The company is on track to surpass $1 billion in revenue this year and estimates it holds nearly 60% of the live commerce market in North America and Europe.

It’s backed by Andreessen Horowitz, Sequoia Capital, CapitalG and others, has raised nearly $975 million and has an $11.5 billion valuation.

Critics say Whatnot’s design encourages overspending and that the company does too little to combat fraud and underage use.

The chaos and speed of the auctions mean there is no meaningful moment of decision, said Mark Leiser, an expert on deceptive design who taught digital law at Leiden University in the Netherlands. He called the cumulative effect a “degradation of consent.”

CEO and co-founder Grant LaFontaine rejected the characterization, saying the company is focused on building a good user experience. He said the company reviews negative comments and data every two weeks and works to address problems. LaFontaine pointed to the app’s rating in the Apple app store, now at 4.7, and said addiction and overspending haven’t registered as significant problems in external and internal data. The company said it has taken steps to fight fraud.

“I don’t want to build a thing that’s going to f— people. I don’t get joy from that,” said LaFontaine in an interview. “We legitimately, when we see a problem, just try to solve the problems.”

He said Whatnot last year introduced optional account controls to add spending limits and watch-time caps. Last week, it started rolling out an additional tool that pauses spending immediately.

Whatnot plans to test an optional passcode-restricted buying step to create more friction before purchase. It will also test flagging information on its spending-limit tools to users who show a sudden spike in spending velocity, he said. Last year, the company doubled the size of its trust and safety team, now about a third of its around 1,200 employees, said a spokeswoman.

“I don’t want a company telling you what to do with [your] money,” said LaFontaine. “But if there are people who are overspending, we want to let them know how to manage that.”

‘I paid more, chat!’

Whatnot has had a meteoric rise for an app that started as a place to buy and sell Funko Pop collectible figurines. LaFontaine and his co-founder, Logan Head, launched Whatnot in 2019 as a way to move their childhood love of trading collectibles into the modern era. LaFontaine described buying and selling Pokémon cards as a kid using money orders through the mail.

They drew Silicon Valley investors, and the pair added Pokémon and sports cards, coins and eventually fashion, electronics and a wide range of other items, including knives, horse tack and live plants.

The company collects an average of about 6% of every sale globally, said the spokeswoman. Around $8 billion worth of goods was sold through the platform in 2025, more than double the prior year, according to company statements.

LaFontaine said the founders stumbled onto the live auction format that dominates the platform—they also host some fixed price sales—when they saw people auctioning Funko Pops during a livestream on Instagram.

Live app-based commerce wasn’t common in the U.S. but had already found momentum in China thanks to the growth of platforms such as Alibaba’s Taobao Live. The value of goods sold through China’s live-commerce market hit around $900 billion in 2025, according to a NielsenIQ analysis.

Whatnot now hosts more than 550,000 hours of live shows each week.

Competitors have followed and are growing fast, although Whatnot has a significant head start. TikTok Shop—a side business to the social-media platform—added live auctions last year, and Fanatics Live offers collectible sports card auctions backed by the sports merchandise giant. EBay also has a live auction option for certain categories of goods such as collectibles.

The Whatnot auctions are events—sellers are personalities who fire up bids, chats buzz with hundreds of buyers, and the animating pressure is often the same: bid now or lose out.

During a recent Pokémon card auction, electronic dance music blared as a fast-talking host flashed a card at the camera. He let out a yelp. The Zekrom card—a black dragon Pokémon—was rare and in near mint condition.

“Wow, chat, I’ll tell you what I paid for this after bidding,” said the host.

The bidding opened at $1. A 45-second countdown clock started ticking. Whichever bidder was in the lead when the time ran out would win. Bids rose fast, so rather than type a custom bid, many buyers swiped the yellow bar at the bottom of the screen, which automatically submits an offer a few dollars over the current top bid.

With five seconds left, the bid sat at $160. “Holy f—! This is such a steal. I paid more, chat!” the host yelled. At the last moment, the price jumped to $170.

Amid the chaos, there was little time to research online, where the card in that condition regularly sells for less than $80.

Designer deals

Fashion buyers alone purchased more than 12 million items a month last year, the company said. Fashion and beauty are the fastest-growing categories on Whatnot.

Sellers—many of whom have earned devoted followings for their style and ability to source coveted fashions—put up a mixture of new and secondhand items.

Julie Johnson, a 58-year-old event planner, discovered the app about three years ago as a place to grab deals on designer fashion. She said she has enjoyed meeting people through the app—a common refrain among users who say they have bonded with others over obscure interests—but wishes she used it less. “It’s a love-hate relationship,” she said.

Johnson estimates she spends around six hours a day watching live shows on her phone, often as background noise while she works. Over three years she has spent around $120,000, she said, mostly on clothing and shoes, often with the intent to resell items for profit. Each month, she pays around $400 for a storage unit to keep the goods and resells around $3,000 worth through Whatnot and Poshmark, another resale platform. She said she breaks even on her purchases.

“I’m totally addicted to it, and it’s weird because I don’t drink. I never did drugs. I don’t have an addictive personality,” she said.

Some buyers planning to resell run into trouble. Joe Thompson joined the app to reconnect with his childhood hobby of coin collecting. The 53-year-old nurse heard stories of people making thousands spotting deals on the platform. He planned to buy undervalued Morgan silver dollars—iconic coins with a buzzing collector market—get them professionally graded and flip them for profit.

Within five months, his entire 401(k) was drained, and he maxed out all 13 of his credit cards.

The coins came back from professional grading services worth far less than he had paid. The seller, it turned out, had been auctioning coins that had been cleaned or artificially altered—a serious flaw that graders flag and collectors shun, rendering the coins nearly impossible to resell at a profit.

On Thompson’s birthday this March, he enrolled in a debt relief program. His credit score had cratered from 753 to 563 and he was close to $75,000 in debt.

Thompson said he operates six ghost accounts where he writes in the chat during sales to warn buyers of potentially shady sales.

Whatnot said it doesn’t allow products or prices to be misrepresented, and will refund buyers and ban sellers for breaking those rules, according to the company spokeswoman. It records all sales to verify buyers’ complaints of a seller who has misrepresented the value of an item, she said.

Thompson didn’t raise the issue to the company because he said it was months before he understood from the grading services the true value of the coins.

Police have charged sellers with moving a wide range of stolen goods on Whatnot, including clothing from SKIMS and Alo, Dyson and Milwaukee Tool, beauty products and Lego sets.

In October, Los Angeles police raided the Santa Monica warehouse of CoolKicks, a popular sneaker reseller, while its co-founder Adeel Shams was streaming live on Whatnot. Police said they recovered more than 2,100 pairs of Nike shoes and 150 cartons of clothing worth an estimated $500,000. Shams was booked on a felony count of receiving known stolen property.

CoolKicks said it had purchased the merchandise in good faith and had no knowledge the goods were stolen. Shams didn’t respond to requests for comment.

Whatnot has cracked down on fake goods and shill bidding—in which the seller’s associates bid up auctions. It said it tightened its seller vetting process, introduced a policy to reimburse buyers who win high-value items that sellers fail to deliver and mandated that all repack boxes be manufacturer-sealed and verified before sale.

Whatnot also said it’s considering additional age verification. Currently, sellers must be at least 18 and show ID, or have parental permission, while buyers aren’t required to show ID.

“As a business gets bigger, there are unique challenges that pop up, so I’m not naive to those things and spend a lot of time just making sure we’re fixing things,” said LaFontaine. It’s a “tricky set of problems.”

Holy grail of trading cards

Some of Whatnot’s most dramatic moments come during the platform’s so-called breaks.

Buyers pay a set amount for a designated share of an unopened box of sports cards—for example, for a basketball pack, one might get the Spurs, another the Knicks, etc. They find out what they’ve won only when the breaker—who also doesn’t know what cards are in the pack—rips it open live on camera. You might win a card worth $1, or one worth thousands or more.

The biggest breaks, which can also cover coins and bullion, livestream around midnight on Fridays and Saturdays, hyped up like parties.

In 2022, a card break on Whatnot produced one of collecting’s most cinematic reveals. The search was on for the Panini Flawless Triple Logoman—the holy grail of trading cards, a one of a kind featuring three NBA logos cut from jerseys worn by LeBron James when playing for the three different teams. Whatnot promised a Lamborghini to anyone who sold it through its app.

One Friday night that May, roughly 1,600 people watched live as a breaker opened a sealed case of NBA cards. A few dozen buyers had each paid a fixed buy-in price and were assigned to a team.

The prized Logoman card was pulled from a pack. Hysteria erupted, with the breakers screaming and jumping on camera and the chat filling with expletives. The three users who held the Lakers, Cavaliers and Heat slots had won the card. They sold it later that year for $2.4 million—and the breaker took Whatnot up on its offer of the cash equivalent for the Lamborghini.

“It’s like being at the casino and watching the guy who just won a hand pay on the slots,” said Zach Duncan, a 33-year-old buyer from Washington state, referring to a win so big it requires a casino employee to pay it out. “You think, ‘Well, maybe my machine’s next.’”

Sports and trading cards ranked as Whatnot’s bestselling categories in the U.S. in 2025. Whatnot said that sellers who break only make up 4% of sellers on the platform but declined to provide numbers on how much revenue that subset generates.

Earlier this year, Paul Lesko, a consumer protection attorney, filed arbitration demands against Whatnot on behalf of more than 70 clients. His complaint, shared with The Wall Street Journal, alleges that Whatnot’s randomized card breaks constitute illegal lotteries under California law, that the company has knowingly facilitated fraudulent practices by its sellers and that it is operating a criminal enterprise in violation of racketeering laws. The complaint claimed Whatnot operates an online casino “without providing the safeguards required of regulated gambling operations.”

The Whatnot spokeswoman said the company absolutely rejects that characterization. “Gambling isn’t allowed on Whatnot, and we strictly enforce this policy,” she said. “One of the main functions of that is you walk away with a card.” Part of gambling, she said, is that you put in money, and then you could walk away with nothing. That is “a massive difference” from Whatnot, she said.

Last year, Alyx Effron launched Collectors MD, a peer support organization for himself and other collectors struggling with compulsive spending. He said he tried Gamblers Anonymous, but people there didn’t see the connection between a shopping app and gambling. “They didn’t understand how something like sports cards or Pokémon could be compared to traditional gambling,” he said.

Harding, the sports card collector who is facing a divorce, would swipe and bid in live auctions, many of them card breaks, into the early hours of the morning after his family went to sleep. “It was every night,” said Harding. “Every single night.”

He had started small in late 2024 with a few hundred dollars a bid. But by the end of January 2025, he was spending as much as $12,000 a day. When he nabbed an undervalued card, he tried to replicate that exhilarated feeling by bidding in more auctions. When he blew hundreds on a dud, he kept participating, trying to recoup. He would sell some cards to cover losses but couldn’t keep up with the pace of his spending.

“I was always justifying to myself to spend more money,” he said. “I liked the game.”

Within a month, all his personal credit cards were maxed out and he owed friends and other lenders—who had approved him when he had a sterling credit history. One night, when one of his favorite sellers urged him to join, he typed his employer’s corporate card into Whatnot’s payment page.

His wife confronted him weeks later after noticing pages missing from a credit report he had doctored to hide the loans. Harding came clean. When he downloaded his full history from his Whatnot account—shared with the Journal—and added up the hundreds of purchases, the grand total was $1,362,687.31.

The reckoning was swift: Harding resigned from his job and his marriage fell apart. To repay his former employer and his creditors, he emptied his retirement account and sold his house, his car and the cards. But he wasn’t completely done with Whatnot: This year, he said, he spent more than $37,000, with money borrowed from a friend and credit cards he had worked to pay down.

Write to Hanna Krueger at hanna.krueger@wsj.com and Sarah Nassauer at Sarah.Nassauer@wsj.com

Sean Harding, who spent almost $1.4 million on Whatnot, at home last month.

Sean Harding downloaded Whatnot, a live-shopping app, after rekindling his childhood baseball-card collecting hobby.

Within four months, the 45-year-old accountant had spent almost $1.4 million—from his savings, personal loans, money borrowed from a friend and finally from his employer’s company credit card. When his wife discovered the full tally, she filed for divorce.

“I just kept telling myself one more time, then I’d sell it all and make all my money back,” Harding said. “But it was so easy to just swipe right. You don’t even remember how many times you’ve done it.”

Seven-year-old Whatnot is one of the fastest-growing shopping platforms in America. It allows people to bid, around the clock, on trading cards, squishy toys, designer fashion and instant ramen, auctioned live in high-energy shows within the app.

It has tapped into the addictive qualities of social media, with opportunities fed to you in an algorithm-controlled scroll. Often, users don’t search for a particular item, but instead hope to hit on something by being on the app at the right time.

The design supercharges traditional shopping sites such as eBay and Amazon with high-pressure countdown auctions, often run by hosts who urge buyers to bid higher and faster. The most feverish shows are built around “breaks,” where a person buys an opportunity to win an unknown, potentially valuable, collectible. All the while, emotionally charged chat feeds can amp up the competition.

Little slows down a decision to spend, which comes with one swipe and no additional confirmation or checkout screen.

Whatnot doesn’t disclose total users but said it added 20 million new accounts in 2025. The company is on track to surpass $1 billion in revenue this year and estimates it holds nearly 60% of the live commerce market in North America and Europe.

It’s backed by Andreessen Horowitz, Sequoia Capital, CapitalG and others, has raised nearly $975 million and has an $11.5 billion valuation.

Critics say Whatnot’s design encourages overspending and that the company does too little to combat fraud and underage use.

The chaos and speed of the auctions mean there is no meaningful moment of decision, said Mark Leiser, an expert on deceptive design who taught digital law at Leiden University in the Netherlands. He called the cumulative effect a “degradation of consent.”

CEO and co-founder Grant LaFontaine rejected the characterization, saying the company is focused on building a good user experience. He said the company reviews negative comments and data every two weeks and works to address problems. LaFontaine pointed to the app’s rating in the Apple app store, now at 4.7, and said addiction and overspending haven’t registered as significant problems in external and internal data. The company said it has taken steps to fight fraud.

“I don’t want to build a thing that’s going to f— people. I don’t get joy from that,” said LaFontaine in an interview. “We legitimately, when we see a problem, just try to solve the problems.”

He said Whatnot last year introduced optional account controls to add spending limits and watch-time caps. Last week, it started rolling out an additional tool that pauses spending immediately.

Whatnot plans to test an optional passcode-restricted buying step to create more friction before purchase. It will also test flagging information on its spending-limit tools to users who show a sudden spike in spending velocity, he said. Last year, the company doubled the size of its trust and safety team, now about a third of its around 1,200 employees, said a spokeswoman.

“I don’t want a company telling you what to do with [your] money,” said LaFontaine. “But if there are people who are overspending, we want to let them know how to manage that.”

‘I paid more, chat!’

Whatnot has had a meteoric rise for an app that started as a place to buy and sell Funko Pop collectible figurines. LaFontaine and his co-founder, Logan Head, launched Whatnot in 2019 as a way to move their childhood love of trading collectibles into the modern era. LaFontaine described buying and selling Pokémon cards as a kid using money orders through the mail.

They drew Silicon Valley investors, and the pair added Pokémon and sports cards, coins and eventually fashion, electronics and a wide range of other items, including knives, horse tack and live plants.

The company collects an average of about 6% of every sale globally, said the spokeswoman. Around $8 billion worth of goods was sold through the platform in 2025, more than double the prior year, according to company statements.

LaFontaine said the founders stumbled onto the live auction format that dominates the platform—they also host some fixed price sales—when they saw people auctioning Funko Pops during a livestream on Instagram.

Live app-based commerce wasn’t common in the U.S. but had already found momentum in China thanks to the growth of platforms such as Alibaba’s Taobao Live. The value of goods sold through China’s live-commerce market hit around $900 billion in 2025, according to a NielsenIQ analysis.

Whatnot now hosts more than 550,000 hours of live shows each week.

Competitors have followed and are growing fast, although Whatnot has a significant head start. TikTok Shop—a side business to the social-media platform—added live auctions last year, and Fanatics Live offers collectible sports card auctions backed by the sports merchandise giant. EBay also has a live auction option for certain categories of goods such as collectibles.

The Whatnot auctions are events—sellers are personalities who fire up bids, chats buzz with hundreds of buyers, and the animating pressure is often the same: bid now or lose out.

During a recent Pokémon card auction, electronic dance music blared as a fast-talking host flashed a card at the camera. He let out a yelp. The Zekrom card—a black dragon Pokémon—was rare and in near mint condition.

“Wow, chat, I’ll tell you what I paid for this after bidding,” said the host.

The bidding opened at $1. A 45-second countdown clock started ticking. Whichever bidder was in the lead when the time ran out would win. Bids rose fast, so rather than type a custom bid, many buyers swiped the yellow bar at the bottom of the screen, which automatically submits an offer a few dollars over the current top bid.

With five seconds left, the bid sat at $160. “Holy f—! This is such a steal. I paid more, chat!” the host yelled. At the last moment, the price jumped to $170.

Amid the chaos, there was little time to research online, where the card in that condition regularly sells for less than $80.

Designer deals

Fashion buyers alone purchased more than 12 million items a month last year, the company said. Fashion and beauty are the fastest-growing categories on Whatnot.

Sellers—many of whom have earned devoted followings for their style and ability to source coveted fashions—put up a mixture of new and secondhand items.

Julie Johnson, a 58-year-old event planner, discovered the app about three years ago as a place to grab deals on designer fashion. She said she has enjoyed meeting people through the app—a common refrain among users who say they have bonded with others over obscure interests—but wishes she used it less. “It’s a love-hate relationship,” she said.

Johnson estimates she spends around six hours a day watching live shows on her phone, often as background noise while she works. Over three years she has spent around $120,000, she said, mostly on clothing and shoes, often with the intent to resell items for profit. Each month, she pays around $400 for a storage unit to keep the goods and resells around $3,000 worth through Whatnot and Poshmark, another resale platform. She said she breaks even on her purchases.

“I’m totally addicted to it, and it’s weird because I don’t drink. I never did drugs. I don’t have an addictive personality,” she said.

Some buyers planning to resell run into trouble. Joe Thompson joined the app to reconnect with his childhood hobby of coin collecting. The 53-year-old nurse heard stories of people making thousands spotting deals on the platform. He planned to buy undervalued Morgan silver dollars—iconic coins with a buzzing collector market—get them professionally graded and flip them for profit.

Within five months, his entire 401(k) was drained, and he maxed out all 13 of his credit cards.

The coins came back from professional grading services worth far less than he had paid. The seller, it turned out, had been auctioning coins that had been cleaned or artificially altered—a serious flaw that graders flag and collectors shun, rendering the coins nearly impossible to resell at a profit.

On Thompson’s birthday this March, he enrolled in a debt relief program. His credit score had cratered from 753 to 563 and he was close to $75,000 in debt.

Thompson said he operates six ghost accounts where he writes in the chat during sales to warn buyers of potentially shady sales.

Whatnot said it doesn’t allow products or prices to be misrepresented, and will refund buyers and ban sellers for breaking those rules, according to the company spokeswoman. It records all sales to verify buyers’ complaints of a seller who has misrepresented the value of an item, she said.

Thompson didn’t raise the issue to the company because he said it was months before he understood from the grading services the true value of the coins.

Police have charged sellers with moving a wide range of stolen goods on Whatnot, including clothing from SKIMS and Alo, Dyson and Milwaukee Tool, beauty products and Lego sets.

In October, Los Angeles police raided the Santa Monica warehouse of CoolKicks, a popular sneaker reseller, while its co-founder Adeel Shams was streaming live on Whatnot. Police said they recovered more than 2,100 pairs of Nike shoes and 150 cartons of clothing worth an estimated $500,000. Shams was booked on a felony count of receiving known stolen property.

CoolKicks said it had purchased the merchandise in good faith and had no knowledge the goods were stolen. Shams didn’t respond to requests for comment.

Whatnot has cracked down on fake goods and shill bidding—in which the seller’s associates bid up auctions. It said it tightened its seller vetting process, introduced a policy to reimburse buyers who win high-value items that sellers fail to deliver and mandated that all repack boxes be manufacturer-sealed and verified before sale.

Whatnot also said it’s considering additional age verification. Currently, sellers must be at least 18 and show ID, or have parental permission, while buyers aren’t required to show ID.

“As a business gets bigger, there are unique challenges that pop up, so I’m not naive to those things and spend a lot of time just making sure we’re fixing things,” said LaFontaine. It’s a “tricky set of problems.”

Holy grail of trading cards

Some of Whatnot’s most dramatic moments come during the platform’s so-called breaks.

Buyers pay a set amount for a designated share of an unopened box of sports cards—for example, for a basketball pack, one might get the Spurs, another the Knicks, etc. They find out what they’ve won only when the breaker—who also doesn’t know what cards are in the pack—rips it open live on camera. You might win a card worth $1, or one worth thousands or more.

The biggest breaks, which can also cover coins and bullion, livestream around midnight on Fridays and Saturdays, hyped up like parties.

In 2022, a card break on Whatnot produced one of collecting’s most cinematic reveals. The search was on for the Panini Flawless Triple Logoman—the holy grail of trading cards, a one of a kind featuring three NBA logos cut from jerseys worn by LeBron James when playing for the three different teams. Whatnot promised a Lamborghini to anyone who sold it through its app.

One Friday night that May, roughly 1,600 people watched live as a breaker opened a sealed case of NBA cards. A few dozen buyers had each paid a fixed buy-in price and were assigned to a team.

The prized Logoman card was pulled from a pack. Hysteria erupted, with the breakers screaming and jumping on camera and the chat filling with expletives. The three users who held the Lakers, Cavaliers and Heat slots had won the card. They sold it later that year for $2.4 million—and the breaker took Whatnot up on its offer of the cash equivalent for the Lamborghini.

“It’s like being at the casino and watching the guy who just won a hand pay on the slots,” said Zach Duncan, a 33-year-old buyer from Washington state, referring to a win so big it requires a casino employee to pay it out. “You think, ‘Well, maybe my machine’s next.’”

Sports and trading cards ranked as Whatnot’s bestselling categories in the U.S. in 2025. Whatnot said that sellers who break only make up 4% of sellers on the platform but declined to provide numbers on how much revenue that subset generates.

Earlier this year, Paul Lesko, a consumer protection attorney, filed arbitration demands against Whatnot on behalf of more than 70 clients. His complaint, shared with The Wall Street Journal, alleges that Whatnot’s randomized card breaks constitute illegal lotteries under California law, that the company has knowingly facilitated fraudulent practices by its sellers and that it is operating a criminal enterprise in violation of racketeering laws. The complaint claimed Whatnot operates an online casino “without providing the safeguards required of regulated gambling operations.”

The Whatnot spokeswoman said the company absolutely rejects that characterization. “Gambling isn’t allowed on Whatnot, and we strictly enforce this policy,” she said. “One of the main functions of that is you walk away with a card.” Part of gambling, she said, is that you put in money, and then you could walk away with nothing. That is “a massive difference” from Whatnot, she said.

Last year, Alyx Effron launched Collectors MD, a peer support organization for himself and other collectors struggling with compulsive spending. He said he tried Gamblers Anonymous, but people there didn’t see the connection between a shopping app and gambling. “They didn’t understand how something like sports cards or Pokémon could be compared to traditional gambling,” he said.

Harding, the sports card collector who is facing a divorce, would swipe and bid in live auctions, many of them card breaks, into the early hours of the morning after his family went to sleep. “It was every night,” said Harding. “Every single night.”

He had started small in late 2024 with a few hundred dollars a bid. But by the end of January 2025, he was spending as much as $12,000 a day. When he nabbed an undervalued card, he tried to replicate that exhilarated feeling by bidding in more auctions. When he blew hundreds on a dud, he kept participating, trying to recoup. He would sell some cards to cover losses but couldn’t keep up with the pace of his spending.

“I was always justifying to myself to spend more money,” he said. “I liked the game.”

Within a month, all his personal credit cards were maxed out and he owed friends and other lenders—who had approved him when he had a sterling credit history. One night, when one of his favorite sellers urged him to join, he typed his employer’s corporate card into Whatnot’s payment page.

His wife confronted him weeks later after noticing pages missing from a credit report he had doctored to hide the loans. Harding came clean. When he downloaded his full history from his Whatnot account—shared with the Journal—and added up the hundreds of purchases, the grand total was $1,362,687.31.

The reckoning was swift: Harding resigned from his job and his marriage fell apart. To repay his former employer and his creditors, he emptied his retirement account and sold his house, his car and the cards. But he wasn’t completely done with Whatnot: This year, he said, he spent more than $37,000, with money borrowed from a friend and credit cards he had worked to pay down.

Write to Hanna Krueger at hanna.krueger@wsj.com and Sarah Nassauer at Sarah.Nassauer@wsj.com