Polymarket vs Kalshi: what actually differs
Both let you trade on real-world outcomes, but they differ in regulation, settlement, market breadth, and fee structure — and those differences change which one fits your trade.
They look the same and aren't
Both platforms sell binary contracts that pay $1 on a correct outcome. From the outside, an order book on one looks like an order book on the other. The differences show up in what you're allowed to trade, what you're settling in, and what it costs you.
Regulation and settlement
Kalshi operates as a CFTC-regulated designated contract market, settling in US dollars from a bank account. Polymarket runs onchain and settles in USDC, a dollar-denominated stablecoin, which means you're managing a wallet rather than a brokerage balance.
That distinction drives most of the downstream ones. Regulated listing means Kalshi's market catalog moves more deliberately. Onchain settlement means Polymarket can list a market about almost anything within hours of it becoming interesting.
Market breadth
Polymarket tends to have wider coverage of fast-moving, culturally-driven questions — an unfolding news event, an awards show, a crypto price threshold. Kalshi's catalog leans toward economic and structured recurring markets: inflation prints, rate decisions, weather, scheduled political events.
If your edge comes from knowing an obscure domain well, the practical question is simply which platform has listed a market about it — and whether that market has enough volume for your size to fill.
Costs
Compare the total cost of a round trip, not the headline fee. That means the trading or settlement fee, the bid-ask spread you cross going in and coming out, and — on the onchain side — gas and any deposit or withdrawal friction.
A market with a nominally lower fee but a 5¢ spread is more expensive than one with a higher fee and a 1¢ spread. The spread is usually the larger number, and it's the one people forget to count.
The case for watching both
When both platforms list the same question, they don't always agree. Those gaps are where cross-platform analysis earns its keep: a 6¢ divergence on the same underlying event is either a real arbitrage or a signal that the two markets are resolving on subtly different criteria.
Check the resolution language before you assume it's the former. Two markets asking what looks like the same question can settle differently on the edge cases, and the edge cases are exactly where the divergence lives.