Kalshi, Polymarket, and Polymarket US hit $50.59B in combined July volume—a record driven by FIFA World Cup betting—but open interest has since dropped 40%.
Prediction Markets News
The FIFA World Cup pushed prediction market trading to its highest monthly level on record in July. Kalshi, Polymarket, and Polymarket US together recorded $50.59 billion in combined volume for the month, up 7.8% from $46.95 billion in June.
Kalshi accounted for most of that total, posting $37.7 billion for the month, a 14% increase from June. Its single prediction market on the World Cup final between Spain and Argentina drew roughly $1.9 billion in volume. Polymarket's market on the overall tournament winner attracted around $4 billion.
Volumes Shift Between Polymarket Platforms
July's data also revealed a split between Polymarket's two venues. The main, offshore Polymarket platform saw its volume drop 26% to $7.9 billion. At the same time, Polymarket US, the company's domestically regulated platform, grew 54% to $5 billion. The combined Polymarket total, across both platforms, fell from $14 billion to $12.9 billion.
Polymarket US is overseen by the Commodity Futures Trading Commission and removed its waitlist in May, opening access to all US users. Earlier this year, Rutgers University statistician Harry Crane estimated that US traders had accounted for roughly 30% of the main Polymarket platform's volume in the 12 months through April 30, 2026, suggesting some of that activity has since moved to the licensed US version.
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Post-World Cup Activity Cools
The tournament ran from June 11 through July 19, and since its conclusion trading has pulled back. Open interest across all three platforms fell from approximately $2 billion at the start of July to $1.2 billion by month's end, a drop of roughly 40%.
The platforms are also navigating legal pressure in the US. More than a dozen state regulators have accused Kalshi and Polymarket of running unlicensed gambling operations and have moved to block event contracts in their states. Both platforms, along with the CFTC, are contesting those enforcement actions and argue that federal oversight takes precedence over state-level rules.
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