Kalshi captures majority trading volume as prediction market interest falls 83%

The prediction market boom that accompanied the 2026 FIFA World Cup is over. Global search interest in the category has dropped back to roughly where it sat before the tournament kicked off, and combined weekly trading volumes on the two dominant platforms, Kalshi and Polymarket, have fallen below $10B for the first time since June. What’s left behind is a clearer picture of who won the land grab. Kalshi, the CFTC-regulated exchange, captured approximately 83% of notional trading volume among approved US platforms during June and July 2026, cementing a position that will be difficult for competitors to dislodge even as the market contracts. The World Cup sugar rush June 2026 was a monster month for prediction markets. Kalshi alone processed $31.5B in trading volume, an 87% jump from May, driven overwhelmingly by sports markets tied to the tournament. Polymarket, which operates across both US and international markets, posted $13.3B in the same period. Together, the two platforms handled roughly $44.8B in June, nearly doubling their combined $24B figure from April. By early August, the post-tournament hangover had set in. Weekly combined volumes dropped below $10B, and Google Trends...