Polymarket vs Kalshi: what's the difference?

If you have started reading about prediction markets, two names come up again and again: Polymarket and Kalshi. They look similar from the outside — buy Yes/No shares on real-world events, watch the price move as a live probability — but under the hood they are built quite differently. Here is a clear, up-to-date comparison. (New to the idea? Start with what a prediction market is.)

Regulation

This is the biggest difference. Kalshi is a CFTC-regulated exchange in the US — a Designated Contract Market — which is how it offers event contracts to Americans directly and legally. Polymarket started as a crypto-native platform and, after acquiring a CFTC-registered exchange (QCEX), re-entered the US in a regulated form; as of late 2025 its US access is increasingly routed through licensed intermediaries rather than direct wallet connections.

The rules are still moving. On 10 June 2026 the CFTC published a proposed rule for prediction markets covering both platforms, open for public comment. In other words, the regulatory picture is being written right now.

How you fund an account

• Kalshi is dollar-first. You fund with USD (bank transfer, card), and crypto is only supported indirectly through third-party providers.
• Polymarket is crypto-first. Balances and settlement run on USDC on the Polygon network, with trades recorded by smart contracts for transparent, automated settlement.

If you are comfortable with a crypto wallet, Polymarket feels natural. If you would rather never touch crypto, Kalshi's dollar rails are simpler.

Fees

Both use probability-based fee formulas that peak around the 50/50 price. Roughly speaking, Polymarket's taker fee tops out near 0.75% at a 50¢ price (sells are not charged a taker fee), while Kalshi uses a maker-taker model where takers pay more, peaking in the region of ~1.75¢ per contract at 50¢. The practical takeaway: fees are small but not zero, and they bite most on the coin-flip markets.

Who can actually use them

Both are US-focused. Kalshi is unavailable in several US states, and both are wrestling with legal scrutiny over sports contracts. For a European reader the honest answer is that access is complicated and often unclear — neither platform is built around European users, payment methods, or regulation.

Where Outcomer fits

This is exactly the gap we are building Outcomer for: a European-first way to trade the same kinds of outcomes, with clear rules, familiar funding, and education alongside the markets — rather than a wall of unfamiliar pages aimed at a US audience. The mechanics you learn on any of these platforms carry over; the difference is who the product is designed for.

The bottom line

Kalshi is the regulated, dollar-based option; Polymarket is the crypto-native one with deep, fast-moving markets. Both proved their scale during events like the World Cup surge that pushed volumes to a record ~$45B. For Europeans, the more interesting question is not just "which US platform" but "what works here" — and that is the story we care about.

Want to get the hang of it first? On Outcomer you can practise with virtual money — same mechanics, zero risk — before real trading goes live.