Polymarket’s market share drops to 27% as Kalshi surges

The on-chain prediction market that owned 2024 now trails its CFTC-regulated rival by a wide margin Two years ago, Polymarket was essentially the entire prediction market conversation. Now it is a supporting character in Kalshi’s story. According to a widely shared post on X, Polymarket’s share of the market has fallen from 96% to 27% over two years. The same post says Kalshi now trades nearly three times Polymarket’s volume. That is a complete reversal in a sector that barely registered with mainstream traders not long ago. The numbers behind the flip October 2026 data puts the gap in sharp relief. Kalshi logged roughly $65 billion in trading volume for the month. That was about 10% higher than September. Polymarket US, the platform’s American arm, recorded $10 billion in October volume. That is a respectable gain of about 15% month over month. Among US-regulated platforms combined, Kalshi held around 83% of market share in October 2026. Polymarket US sat at roughly 12% to 15% in recent snapshots. Polymarket Global, the original international product, is down in the single digits. Open interest tells a similar story. Open interest is the total value of positions still active, basi...