Kalshi extended its lead over Polymarket in April, posting $14.8 billion in monthly volume as its rival recorded its first decline since August.
Prediction Market Gap Widens In April
The Dune Analytics data, shows, Polymarket volume slid 8.9% to $10.2 billion.
Kalshi climbed roughly 13% from March, when it logged $13.07 billion, widening its monthly lead to $5.8 billion.
Combined volume across major prediction markets reached $29.8 billion in April, a 12.4% gain from $26.5 billion the prior month.
Kalshi has since captured 72.1% of weekly volume through early May, per DeFi Rate. Polymarket's active trader count fell from about 733,000 in March to 643,000 in April, a roughly 12% drop that tracked closely with the volume decline.
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Warren And Wisconsin Tighten Screws
A Polymarket spokesperson attributed part of the slide to a V2 platform upgrade rolled out April 28 that paused trading for an hour and wiped open orders.
"We've let people down, and I'm not going to dress that up," vice president of engineering Josh Stevens told Bloomberg.
Founder Shayne Coplan acknowledged at a Harvard event that the company had at times run "suboptimal" operations.
The slide arrives as Washington scrutiny tightens. Sen. Elizabeth Warren and more than 40 lawmakers wrote to the Commodity Futures Trading Commission in March, urging the agency to treat event contracts as swaps under its jurisdiction. In April, Wisconsin Attorney General Josh Kaul filed suits against both platforms, alleging violations of state sports betting laws.
Sports Tailwinds And AI Entrants
The structural divide between the two venues is part of the story. Polymarket exited the U.S. market in 2022 under a CFTC settlement, then relaunched a domestic app in December 2025 that does not share liquidity with its offshore exchange. Kalshi, fully regulated as a designated contract market, has leaned harder into sports contracts, which account for roughly 85% of its activity once parlay-style products are included.
The Masters tournament alone drove $545 million in notional volume on Kalshi in April, matching its Super Bowl single-game record. AI-native platform Prophet also launched its first live trading tranche in April, with an algorithm acting as a counterparty using real capital.
Earlier this year, a U.S. special forces soldier was charged with using classified information to net more than $400,000 on Polymarket bets tied to the January operation against Venezuelan leader Nicolás Maduro. Through 2025, both venues rode election-year and sporting-event surges to record growth, with lifetime combined volume crossing $150 billion last month.
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