Combined prediction-market volume hit an all-time high of $50.59B in July

July trading across Kalshi, Polymarket and Polymarket US reached a record $50.59 billion, rising 7.8% from June’s $46.95 billion, according to The Block’s data dashboard, as reported by GambleRSS. The headline gain masked divergent results: Kalshi expanded, while growth at Polymarket’s U.S. operation did not offset a decline offshore.

Kalshi leads as Polymarket’s mix changes

Kalshi recorded $37.7 billion in monthly volume, up 14% from June, retaining its lead. Polymarket’s offshore platform fell 26% to $7.9 billion, while Polymarket US increased 54% to $5 billion. Together, the two Polymarket platforms generated $12.9 billion, down from $14 billion.

Polymarket US, which is regulated by the Commodity Futures Trading Commission (CFTC), removed its initial waitlist restrictions in May and opened access to all U.S. users, according to GambleRSS. That provided a legitimate route for U.S. traders who had previously circumvented regional restrictions. Earlier this year, Rutgers University statistician Harry Crane estimated that U.S. traders accounted for about 30% of offshore Polymarket volume over the 12 months ending April 30, 2026.

World Cup activity meets a legal overhang

GambleRSS attributed July’s volume strength to the FIFA World Cup, which ran from June 11 to July 19. Kalshi’s market on the Spain–Argentina final generated roughly $1.9 billion, while Polymarket’s tournament-winner market attracted around $4 billion.

The record turnover was accompanied by a retreat in open interest as the tournament concluded. Across the three platforms, open interest declined from around $2 billion at the beginning of July to $1.2 billion at month-end, according to GambleRSS.

Sports contracts also remain under U.S. legal scrutiny. Over a dozen state regulators have accused Kalshi and Polymarket of offering unlicensed gambling and have acted to block event contracts within their states. The platforms and the CFTC are challenging those actions, arguing that federal oversight takes precedence over state jurisdiction.

What it means for prediction markets

• The aggregate record conceals uneven growth. Kalshi gained volume, but Polymarket’s combined U.S. and offshore total declined despite rapid U.S. expansion.
• Tournament turnover and continuing exposure tell different stories. July’s record volume coincided with lower month-end open interest, making the headline total an incomplete measure of sustained activity.
• U.S. access is an important variable. The waitlist removal preceded Polymarket US’s growth, though the reported figures do not establish how much activity migrated from offshore.
• Jurisdiction remains contested. The dispute over federal and state authority leaves sports-related contracts at the center of the platforms’ legal uncertainty.