Prediction markets — platforms where traders buy contracts tied to the outcomes of real-world events, from elections to sports and economic indicators — set a new all-time high in July, with combined trading volume across Kalshi, Polymarket, and Polymarket US reaching $50.6 billion, according to data published on August 3.

The total represented a 7.8% increase from June's revised figure of $46.95 billion. The original June report had cited $44.8 billion; additional trading data became available after the month closed, raising the baseline.

Kalshi Dominates with $37.7 Billion

Kalshi remained by far the largest platform. It generated $37.7 billion in July volume, up approximately 14% from June, accounting for roughly 74.5% of the combined total across all three venues. Kalshi operates as a federally regulated designated contract market under the Commodity Futures Trading Commission, a status that distinguishes it from offshore competitors and underpins its legal arguments for federal preemption over state gambling law.

Polymarket's two platforms together produced $12.9 billion, down from about $14 billion in June — even as one of the two platforms grew.

Polymarket, Polymarket US, and Kalshi posted combined monthly volume of $50.6 billion in July, an all-time high. Polymarket US volume rose 54% to $5 billion, while Polymarket volume fell… pic.twitter.com/Ujb69YDyAo

— Wu Blockchain (@WuBlockchain) August 3, 2026

Polymarket US Growth Outpaces Offshore Decline

Polymarket US recorded the strongest growth among the three exchanges. Its volume climbed 54% to $5 billion in July, after the platform removed its app waitlist in May, broadening access to U.S. users.

Polymarket's international platform moved in the opposite direction, with volume falling 26% to $7.9 billion — a decline large enough to more than offset Polymarket US gains.

Rutgers University statistician Harry Crane has studied the origins of Polymarket's offshore volume. He estimated that approximately 30% could originate from U.S. traders, with a broader range of 19% to 48%. Crane noted that blockchain transactions do not reveal trader location, meaning his estimates rely on indirect data rather than confirmed customer records.

World Cup Contracts Drive Activity

The FIFA World Cup, held from June 11 through July 19, generated a steady stream of sports contracts throughout the tournament. The influx of sports volume marked a shift for an industry that built much of its early traction around political election contracts before expanding into athletics, entertainment, and economic events. Kalshi's market on the final between Spain and Argentina alone produced about $1.89 billion in volume. Spain won the match 1-0.

Chainalysis separately tracked blockchain-based prediction markets tied to the World Cup, estimating $20 billion in related volume from January through the end of the tournament. According to Chainalysis, approximately 400,000 wallets generated $5.7 billion during the five-week competition, with World Cup markets comprising roughly 63% of all prediction-market activity during that period.

These Chainalysis figures are not directly comparable to the $50.6 billion combined total, as Chainalysis tracked only on-chain activity while the broader dataset includes Kalshi's centralized platform alongside both Polymarket exchanges.

Open interest across all three platforms declined as the tournament concluded, falling from approximately $2 billion in early July to about $1.2 billion by month's end, reflecting the closure of positions as World Cup contracts settled.

Trading volume differs from platform revenue or customer deposits. Traders can buy and sell the same contract multiple times before settlement, inflating volume figures without new capital entering the platform.

Legal Battles Intensify

Legal disputes continue to shape the industry, which operates at the intersection of federal commodities oversight and state gambling regulation. On July 31, New York sued Kalshi, accusing it of operating an unlicensed gambling operation. The state is seeking penalties, forfeiture, and customer restitution, though the claims have not been proven in court.

Four days earlier, a federal judge in Minnesota issued a contrasting ruling, temporarily blocking the state from enforcing its prediction-market law against Kalshi and Polymarket US, citing federal preemption. The judge noted that not every contract on these platforms may qualify as a federally regulated swap, meaning any final ruling could prove narrower than the temporary order.

August will mark the first full month without World Cup contracts driving volume. Traders and platforms are now watching whether sports, political, and economic contracts can sustain activity levels while the New York and Minnesota court cases proceed — proceedings whose outcomes could clarify whether prediction markets fall under federal commodities law or state gambling statutes.