Combined volume on Kalshi and Polymarket roughly doubled from May to July. The World Cup drove the jump, and no other category comes close to sports on either platform.
Prediction markets became famous by calling a presidential election. Their growth is now coming from games.
Combined monthly trading volume on Kalshi and Polymarket reached $53.0 billion in July. That was up from $25.7 billion in May and $2.0 billion in July 2025, a 26-fold increase in a year. June came in at $47.7 billion.
The election month that put the platforms on the map now looks small. In November 2024, when the two sites drew attention for pricing the presidential race, combined volume was $4.7 billion. July's total was more than 11 times that.
Sports is responsible for most of the difference. On both sites, sports now outtrades every other category by a wide distance. Across June and July, when the FIFA World Cup was under way, sports contracts drew $58 billion of trading on Kalshi and nearly $22 billion on Polymarket. In July alone, Kalshi's sports volume came to $31.4 billion. Kalshi's next-biggest category that month was crypto, with about $6 billion.
The comparison with sportsbooks shows how far the shift has gone. In the first quarter of 2026, sports trading on the two platforms was already running at about the same level as the roughly $40 billion Americans bet through legal sportsbooks.
Politics, by contrast, is a comparatively small business on both platforms. Kalshi's contract on control of the Senate traded about $35.7 million in a single day this week, a sliver of a market that turned over $53 billion in a month.
That mix explains where the legal fights are. State attorneys general, including New York's, argue that the platforms run illegal gambling, and the contracts that look most like gambling are the ones driving the volume. Washington takes the opposite view. The Commodity Futures Trading Commission says oversight of the industry belongs to it alone, and New Jersey has asked the Supreme Court to settle the conflict.
The growth has made that question more expensive to answer. A business whose revenue depends on sports contracts has more at stake in a ruling on sports contracts than one built on elections. The Supreme Court's decision on whether to hear New Jersey's petition, in a term that opens , is the first catalyst. August and September volume will show whether the platforms can hold their gains now that the World Cup is over.