Kalshi, Polymarket, and Polymarket US posted a combined $50.59 billion in July trading volume, the highest monthly total on record, according to data published August 3. The figure represents contract trading volume rather than deposits or platform revenue, and marks a 7.8% increase from the revised June total of $46.95 billion.

FIFA World Cup prediction markets were a primary driver of July's activity, as Kalshi and Polymarket continued to face state-level legal challenges over sports event contracts.

World Cup Fuels Trading Activity

Kalshi remained the dominant platform in July, generating $37.7 billion in monthly volume — roughly 74.5% of the combined total and a 14% increase from June. Kalshi launched in 2022 as a CFTC-regulated exchange and has since expanded its event-contract offerings into categories including sports, politics, and economics.

Polymarket's two platforms moved in opposite directions. Polymarket US posted the strongest monthly growth, with volume climbing 54% to $5 billion. Polymarket's international platform, however, saw volume fall 26% to $7.9 billion. Together, the two platforms' combined monthly volume declined from $14 billion to $12.9 billion.

The FIFA World Cup, which ran from June 11 through July 19, contributed significantly to July's trading activity. Kalshi's Spain-Argentina final market generated approximately $1.9 billion, while Polymarket's World Cup winner market attracted roughly $4 billion.

Open interest across the three platforms dropped from about $2 billion at the start of July to roughly $1.2 billion by month-end as World Cup contracts settled.

Polymarket US Expands Access

The volume shift followed Polymarket US removing its waitlist in May, making the Commodity Futures Trading Commission-regulated platform available to all eligible U.S. users. Polymarket had previously operated offshore and settled with the CFTC in 2022 for $1.4 million over allegations of offering unlicensed binary options, after which it restricted U.S. users from its international platform.

Earlier this year, Rutgers University statistician Harry Crane estimated that approximately 30% of Polymarket's offshore volume originated from U.S. traders over the previous 12 months. He noted, however, that blockchain transactions cannot directly identify user locations.

Regulatory Disputes Persist

Despite record trading volumes, legal and regulatory challenges remain unresolved. More than a dozen state regulators have accused Kalshi and Polymarket of operating unlicensed gambling platforms through sports-related contracts.

The companies, along with the CFTC, continue to challenge those enforcement actions, arguing that federal oversight takes precedence over state jurisdiction. The disputes center on whether sports event contracts are regulated commodities under the Commodity Exchange Act or fall under state gambling laws — a question whose resolution could determine the scope of products the platforms may offer nationally. New York filed suit against Kalshi on July 31. Separately, a Minnesota federal judge temporarily blocked state enforcement actions against Kalshi and Polymarket US during an ongoing legal dispute.