Prediction market platform Kalshi said it recorded $500 million in trading volume during the Masters golf tournament.

Cryptopolitan, a blockchain media outlet, reported on April 14 that Kalshi posted on X, formerly Twitter, that it had set a record during the Masters. An image showed $500 million of trading across winner markets, player-specific bets and other side bets on the tournament held in Augusta, Georgia. It said weekend trading rose sharply as money flowed in from retail investors to hedge fund participants.

The figure shows prediction markets are rapidly expanding on the back of sports events. Kalshi had previously disclosed trading volume related to the Super Bowl, and the Masters performance showed market interest and influence have grown further. That is also increasing the intensity of regulation and market monitoring.

Polymarket recently revised its market integrity rules, strengthening standards banning insider trading and market manipulation. The new rules apply to exchanges as well as the decentralised finance sector. They ban trading based on non-public information and the provision of information that violates duties of trust. The ban also covers elected officials or government insiders betting on events they can influence.

If violations are confirmed, measures can include wallet blocking, fines, trading suspensions, account termination and referrals to investigative authorities. In related discussions, Polymarket Chief Legal Officer Neal Kumar (닐 쿠마르) said, "Markets grow on the basis of clarity," adding, "This measure made clear the standards all participants must follow."

Polymarket's move came alongside controversy over suspicious trades. Earlier this year, a user bet $32,000 on the ouster of Venezuela's Maduro hours before the U.S. military moved, and later earned more than $400,000 in profits. The trade fuelled insider trading suspicions because its timing was unusually precise.

Polymarket is also moving beyond rule changes, stepping up crackdowns on startups and developers that promoted copy trading that mimics transactions suspected of using inside information by using the platform's liquidity and data.

Political moves are also continuing. U.S. Representative Richie Torres introduced the 2026 Financial Prediction Market Public Integrity Act and, along with more than 40 Democratic lawmakers, is pushing to outlaw trading that uses major non-public government information. As prediction markets begin to wield influence closer to that of financial markets, legislative discussions are also moving into earnest.

Kalshi has also responded to trading based on non-public information. Kalshi stopped trading by a MrBeast video editor, and fined and banned a California gubernatorial candidate who bet on their own election. It also did not pay out settlement funds in a market linked to the death of Iran's supreme leader, refunded fees and closed out positions at the last traded price.