On-chain action on game day: $2 billion has been wagered—how do on-chain contracts know who won?
The World Cup is about to begin. On the opening day, two events happen almost simultaneously.
One thing is money. Before the tournament began, the combined trading volume of the two "World Cup Champion" contracts on Kalshi and Polymarket exceeded $2 billion—without a single match having been played [1]. Another is prestige. Two days before the tournament started, the crypto exchange Kraken was announced by FIFA as an official cryptocurrency exchange sponsor (Supporter level, covering North America and Europe; financial terms undisclosed) [5][6][7].
But what this article truly wants to ask is a more fundamental question, one sports media won’t touch: When the World Cup actually kicks off, how do these on-chain contracts actually “know” who won? How does the price move with the match? How are contracts handled when a team is eliminated? Who determines the outcome? And how much of the billions wagered is real? This is the first day prediction markets move from “static pre-game numbers” into “live event operation.”
Following up on the previous episode (the static data overview before the event), this episode covers: at this very moment, how this machine truly comes to life.
Data as of June 11, 2026. All prices and volumes are subject to change and may differ at the time of publication. This article does not predict any outcomes of events.
Act One · How the $2B Was Built—and Which $2B
First, break apart the most eye-catching number.
By the start of the tournament, the "World Cup Champion" contract on Polymarket had accumulated approximately $1.9 billion in trading volume since its opening on July 2, 2025 [4]; the same contract on Kalshi added another $132 million; together, they surpassed $2 billion for the first time on June 8 (two days before the tournament began) [1]. If the scope is expanded to include all platforms and all World Cup-related contracts—not just the "champion" outcome—the total trading volume across the entire sector has exceeded $3 billion [3].
Connect it back to the previous episode: On June 5, we recorded Polymarket at 1.6 billion on a single platform. Six days later, the same metric had reached 1.9 billion. Using the same ruler, the curve remains continuous.
Looking at the broader market, Pew Research Center data shows that the combined monthly trading volume of Kalshi and Polymarket rose from under $5 billion in September 2025 to approximately $24 billion in April 2026; for comparison, the average monthly betting volume in legal U.S. sports betting last year was around $14 billion. The size of prediction markets has now surpassed traditional sports betting [3].
As for how the market currently views the championship winner—as of June 10, Spain is priced at approximately 16.5% on Polymarket and 17.4% on Kalshi, France follows closely at around 16%, England and Portugal each at about 11%, defending champions Argentina at roughly 9%, and Brazil at 8% [1]. These are merely the market’s current pricing, not predictions, and certainly not the judgment of this article.
Act Two ·逐场合约: How the machine operates after kickoff
Two billion is for the long-term contract on "Who Will Win." But what truly comes alive each day after the match starts are the individual match contracts covering every game.
The betting markets for match day have been posted (below are current market prices, provided as a snapshot only and not constituting any prediction): In the moneyline contracts for the opening match, home team Mexico is priced as the heaviest favorite of the day; the other match on the same day, South Korea vs. Czech Republic, is viewed by the market as the closest of the four opening games, with South Korea at approximately 37 cents, Czech Republic at 34 cents, and the draw at 32 cents—nearly a three-way tie; meanwhile, the USA vs. Paraguay matchup is essentially even—USA at approximately 50 cents, Paraguay at 23 cents, and the draw at 29 cents. For all four opening matches, the "total goals" contracts favor under, with the implied probability of "under 2.5 goals" ranging between 57% and 59% [2][8].
The logic is the same for every contract: the price fluctuates between 1 cent and 99 cents and directly represents the implied probability—50 cents means the market assigns approximately a 50% probability. As the game progresses and the score changes, the price moves accordingly.
Here is a mechanism that occurs repeatedly after the tournament begins but is rarely explained: elimination to zero. When a team is mathematically eliminated from winning the championship, its "Win Yes" contract immediately resets to zero and settles as "No" [4]. As the group stage progresses, the first teams to be eliminated will emerge—marking the first large-scale, real-world settlement of these championship contracts. This is one of the most important on-chain moments to watch during the tournament.
Act Three · How On-Chain Contracts "Know" Who Won: Two Paradigms
This is the thing that should be explained the most on game day, yet almost no one explains it.
An on-chain contract is just a piece of code. It doesn’t watch the game. So when Mexico and South Africa finish playing, how does the on-chain contract that says "Mexico wins" know what actually happened in the real world and then pay the people who guessed correctly?
The answer is called an oracle—a bridge that feeds real-world information into on-chain contracts. Currently, the industry has two distinct paradigms addressing this question.
First type: UMA’s “Optimistic Oracle,” primarily used by Polymarket (accounting for approximately 78% of its markets). “Optimistic” means: initially assume the submitted result is correct, then allow a window of time for others to challenge it. The process works as follows—a whitelisted proposer stakes 750 PUSD as collateral and submits the result “Mexico wins”; next, there is a 2-hour challenge window during which anyone can stake the same amount to dispute it. If no one challenges, the market automatically settles on this result: each correct contract instantly pays out $1, while incorrect ones expire to zero, with no manual claim required. If someone does challenge, the dispute escalates to a vote by UMA token holders for resolution [9].
This whitelist has a clear origin: In March 2025, a market called "Ukraine Minerals" suffered a governance attack, affecting approximately $7 million, exposing the weakness of a structure where anyone could submit results. In response, in August, UMA passed proposal UMIP-189, restricting proposal rights to a whitelist—starting with 37 addresses and expanding to 177 by November 2025, with eligibility requiring at least five proposals in the past six months and an accuracy rate above 95%. However, it’s important to emphasize: the right to challenge remains open to everyone—you do not need to be on the whitelist to contest any result you believe is incorrect [10].
Second: Chainlink’s “multi-source aggregation,” used by FIFA official partner ADI Predictstreet and Myriad (Polymarket also has approximately 15% of its market using Chainlink). On June 9, ADI Predictstreet announced the adoption of Chainlink as its exclusive oracle infrastructure to actively aggregate match results from multiple data sources, automatically creating markets, settling, and processing payments, with a focus on “dispute-free, instant settlement” [11].
Putting the two paradigms side by side makes the difference clear: when faced with the question "Who determines the truth?", UMA's answer is "Trust first, leave a challenge window, and vote in case of dispute"; Chainlink's answer is "Aggregate data from multiple authoritative sources, auto-feed prices, and leave almost no room for dispute." This isn't an either/or choice—Polymarket primarily uses UMA, but some markets also integrate Chainlink; for events like World Cup results—clear and unambiguous—both paradigms are significantly safer than fuzzy political or geopolitical markets.
ESPN will tell you who won. But how does an on-chain contract "know" who won—two entirely different decentralized systems are at work behind the scenes.
Act Four · Of these billions, how much is real
The series has been discussing how prediction markets grow. But as content that avoids casino-style narratives, we must add a sobering question to this "$2 billion" story.
First, let’s look at how the funds are settled. All these contracts are denominated in USDC, a USD-pegged stablecoin, and settled on the Polygon chain [12]. A telling detail: a contract that is almost certain to win often trades between $0.995 and $0.999 before final settlement—because some traders prefer to sell immediately at $0.999 rather than wait several hours for the oracle process to complete and receive the full $1 [9]. This is the immediacy provided by the stablecoin settlement layer.
But then comes the sobering counterquestion: While the benefits of the chain are that everything is publicly visible and open to audit, precisely because it is public, the problems are also visible: Researchers at Columbia University estimated in a study that approximately 25% of Polymarket’s historical trading volume may be “wash trading” — where the same party buys and sells to artificially inflate trading numbers [13]; in sports markets, this proportion has been around 45% overall, and reached as high as 90% in one week in 2024 [14].
It must be emphasized that this is an estimate from third-party research, not official platform data, and the methodology is controversial—such as a statistics professor at Rutgers University who argues that the narrative around manipulation has been exaggerated and even biased. But even if you discount the estimate, it still reminds us of one thing: when you see the number "2 billion," it measures the scale of market activity, not $2 billion in genuine, distinct transactions from different individuals.
The platform is also taking action. On June 10, Kalshi introduced new anti-insider trading rules—requiring traders to disclose their employer information for markets with higher manipulation risk, and implementing a market risk scoring system [15]. This is a necessary step for the maturation of prediction markets.
Closing · One bet, two roles
Finally, return to the most fundamental question—what exactly are these contracts in your location?
Someone put it very plainly: Betting $100 on France winning the championship on a sports betting platform like DraftKings is considered "gambling," regulated by individual states and strictly geofenced; but buying a "France will win the championship" contract on Kalshi is considered legal "trading" for adults across all 50 U.S. states. The same wager, the same screams during penalty kicks—yet the legal status is vastly different [16].
This is precisely the core regulatory divergence discussed in the previous episode of this series: prediction markets follow the U.S. CFTC’s “event contract” pathway, while sports betting follows state licensing pathways. Yet over these past few days, states such as Minnesota, New Mexico, and Nevada continue to argue that these so-called prediction markets are, in essence, “disguised sports betting.” The legal battle over “what it really is” is far from over.
The same World Cup contract may have completely different legal status in different jurisdictions. Please verify the rules applicable in your location.
The whistle has blown, and this machine—backed by billions, priced in stablecoins, adjudicated by oracles, and watched by regulators—has finally begun to operate. Over the coming month, we’ll witness its first real settlement, its first true zero-out, and after the final on July 20, we’ll look back to see whether the market or those supercomputing models got it right.
How it works may be more worth watching than who ultimately wins.
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