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, basically the money currently sitting on the table rather than money that has already changed hands. Kalshi carried about $2.05 billion in open interest in October. Polymarket US held about $384 million.
The share data lines up with a long, steady slide rather than a sudden collapse. Polymarket held about 95% of the market in September 2024. Kalshi climbed from single-digit share to more than 60% by 2025, then held at 75% to 80% or higher throughout 2026.
How Polymarket lost its grip
Polymarket built its reputation during the 2024 US election cycle. It runs on-chain, meaning trades settle on a blockchain using crypto rather than through a traditional brokerage. For a while, that crypto-native model gave it a near-monopoly on serious prediction market activity.
Kalshi took a different route. It operates as a CFTC-regulated exchange, which means it answers to the same federal agency that oversees futures markets.
Three factors stand out in Kalshi’s rise. The first is regulatory clarity, which made the platform easier for mainstream users and partners to touch. The second is distribution: partnerships with retail brokerages Robinhood and Coinbase put Kalshi contracts in front of millions of existing accounts. The third is product breadth, with Kalshi expanding into sports and combo or parlay-style bets.
Polymarket’s response has been its US branch, which is growing. But its international volumes are shrinking, and the domestic business remains much smaller than Kalshi’s American operation.
What this means for the prediction market race
The Coinbase partnership adds a twist for crypto watchers. A major crypto exchange is helping distribute a regulated, non-blockchain prediction product.
For Polymarket, the on-chain model that powered its early dominance now looks like a narrower lane. Its US arm posted faster monthly growth than Kalshi in October, around 15% versus around 10%. But percentage growth on a $10 billion base and a $65 billion base produce very different absolute dollar gains, so the distance in raw volume is still widening for now.
Prediction market activity tends to spike around big events like elections and major sports seasons. October 2026 brought record-high open interest across the sector heading into the US midterm elections. Polymarket’s 2024 peak came during an election cycle. Kalshi now appears positioned to capture the bulk of this one.
For traders and investors watching the sector, a few things are worth tracking. The first is whether Polymarket US can keep compounding faster than Kalshi after the midterm surge fades. The second is whether more brokerages follow Robinhood and Coinbase into distribution deals, and with whom. The third is how regulators treat expanding categories like sports and parlay contracts, since that product mix has been central to Kalshi’s growth.
For now, the scoreboard is lopsided. The platform that once owned roughly 95% of the market has watched its share shrink to a fraction of that in about two years, while a regulated rival with brokerage distribution took the lead and kept extending it.
