Kalshi closed June with more than 31 billion dollars in trading volume, an 87% jump from May. Polymarket added 10.8 billion in the same month, a record for the platform. Combined, plus its regulated US arm, the total reached 44.8 billion dollars. No other sporting event had moved that amount of money through prediction markets.
The source of the jump has a name: the 2026 World Cup. The tournament kicked off on June 11, and Kalshi has kept a daily volume above 1 billion dollars since. Apptopia analysts recorded something more telling than the money itself: Kalshi’s daily active users grew 36% between June 15 and June 30, while traditional sportsbooks like DraftKings and FanDuel lost between 36% and 41% off their early peak in the same window.
The pattern matters because it reverses the usual logic of a soccer tournament. In a normal World Cup, betting interest concentrates at kickoff and fades as the calendar advances. Here the opposite happened: World Cup prediction markets gained users right as traditional sportsbooks started losing them. Kalshi and Polymarket captured 78.5% of betting app downloads in June, up from just 6% combined a year earlier.
Product structure explains much of that retention. Kalshi spreads its volume across match-by-match contracts, with hundreds of active markets running at once. Polymarket concentrates activity in tournament-wide contracts, chiefly the World Cup winner market, which holds 3.41 billion dollars in cumulative volume on that platform alone.
The United States offers a case study in that behavior
The round of 16 match between the United States and Belgium moved 64 million dollars on Kalshi and 122 million on Polymarket, even though both platforms priced the US team at only 3% to 4.3% probability of winning the tournament outright. Money did not follow title probability; it followed immediate interest in the match being played that night.
That mismatch between volume and probability has a simple reading. A prediction market does not measure only how likely an outcome is. It also measures how many people want an open position on an event about to happen, regardless of whether that position reflects a realistic expectation of winning.
France reached the semifinals with a perfect group-stage record, including a 4-1 win over Norway featuring an Ousmane Dembélé first-half hat-trick. Kalshi prices France at 33.1% probability of winning the World Cup, followed by Argentina at 17.9%, England at 14.1%, and Spain at 12.6%. A France-Argentina final is the most heavily priced combination on both platforms, an exact repeat of the 2022 Qatar final, which Argentina won on penalties.
That is where a technical point comes in that any newcomer to World Cup prediction markets needs to understand before trading. The tournament winner contract settles on who lifts the trophy, regardless of whether the final is decided in regulation, extra time, or penalties. But the match-by-match contract in the knockout stage works differently: it settles on the 90-minute score plus stoppage time, and does not include extra time or penalties.
That distinction is not a minor detail when a third of the knockout matches in Qatar 2022 were decided outside regulation time. A trader who buys the wrong contract during the World Cup knockout stage can lose a position even if the team keeps advancing.
The rule applies equally on Kalshi and Polymarket; neither platform hides it, but it is not obvious to someone carrying over the group-stage habit, where a draw counts as a valid outcome and there is no ambiguity to worry about.
Another figure puts the size of this phenomenon in perspective against the rest of each platform’s business. On Polymarket, sports accounted for 56.5% of total June volume, while politics fell to 831 million dollars. A year earlier, elections drove much of these platforms’ growth; today soccer has overtaken it entirely, even on a venue built around political and financial markets.
Kalshi leads on market share, with 58% of total flow against Polymarket’s 28%, according to Binance Research data cited by industry outlets. Structural difference explains the gap again: Kalshi charges a fee on every individual contract and multiplies that fee across hundreds of active markets per matchday. Polymarket concentrates activity in fewer, larger contracts, with lower fee frequency per trade.
An open question remains about what happens after July 19, the tournament’s closing date. Kalshi and Polymarket already face legal scrutiny in more than a dozen US states, which accuse them of offering unlicensed sports betting under the guise of prediction contracts.
The World Cup proved these platforms can acquire massive user bases fast; it has not yet proved those users keep trading once the final ends and there is no match to bet on the following night.
For anyone deciding to trade World Cup prediction markets during the remaining rounds, two checks up front prevent most common mistakes. First, confirm whether the contract settles on the 90-minute result or on advancement to the next round, since these are separate markets with separate settlement rules.
Second, check each platform’s resolution source: Kalshi relies on FIFA and ESPN as reference, while Polymarket declares FIFA as primary source with credible reporting as backup. Neither rule changes based on how much money moves through the match, or how many people are watching that night.
