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 data confirmed what the order books were already showing: both peaks in global search interest for prediction markets landed squarely on tournament dates, and the decline since has been a clean reversion to the mean.

Why Kalshi is pulling away

Kalshi operates under direct CFTC oversight, which gives it access to a class of institutional and retail participants who won’t touch unregulated venues. That regulatory moat proved decisive during the World Cup, when mainstream sports bettors flooded into prediction markets for the first time at scale. Many of them chose the platform that looked most like a traditional exchange.

Polymarket, built on blockchain infrastructure, has historically drawn a more crypto-native audience comfortable with self-custody and decentralized settlement. Its $13.3B June figure is nothing to dismiss, but it represents a smaller share of a market that Kalshi is defining in its own image.

Kalshi’s market share during the World Cup, hovering between 80% and 90% of CFTC-approved platform volume, suggests that when prediction markets go mainstream, they do so through traditional financial rails. Polymarket’s strength lies in markets that regulated exchanges either can’t or won’t list, from geopolitical outcomes to niche crypto events.

The normalization problem

Prediction markets are inherently event-driven. They spike around elections, major sports tournaments, and geopolitical inflection points, then settle back to baseline. The 2024 US presidential election produced a similar pattern on Polymarket, which saw volumes surge and then retreat once the outcome was settled.

Kalshi has been expanding its contract offerings aggressively, moving into weather events, economic data releases, and cultural markets. Polymarket has leaned into its permissionless listing model, allowing traders to create markets on almost anything.

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