Polymarket and Kalshi both list event contracts that pay $1 if an outcome happens, but they differ in structure: Kalshi is a US exchange regulated by the CFTC and trades in dollars, while Polymarket's main platform is a crypto venue on Polygon that settles in pUSD and does not let US users open positions. Nimb maps Polymarket only and has no commercial relationship with Kalshi.
What is the difference between Polymarket and Kalshi?
The contract is the same idea on both: a share pays $1 if an outcome happens and $0 if not, so the price reads as a chance (see what are prediction markets). The difference is the wrapper around it: who regulates the venue, who may use it, what money it uses, how it charges and how it settles a question. Facts below are as of 2026-11-07; both venues change their products often, so check each one's own pages before you rely on a detail.
How do Polymarket and Kalshi compare at a glance?
| Polymarket (international) | Kalshi | |
|---|---|---|
| Regulator and structure | Crypto platform with on-chain settlement on Polygon; not a CFTC-regulated venue for its international users. A separate CFTC-regulated US exchange, Polymarket US, operates through the former QCEX. | CFTC-designated contract market (KalshiEX LLC) since November 2020 |
| Eligible users | Close-only in the US, the UK, France and about 35 other countries; blocked in sanctioned places; location checked before orders | US residents; since October 2025 also many countries outside the US, with a list of restricted jurisdictions |
| Collateral | pUSD, a USDC-backed token on Polygon, held in your own wallet | US dollars in a Kalshi account; deposits by bank and card, with crypto deposits also offered |
| Custody | Self-custody: positions and pUSD sit in a wallet you control | Held by the exchange and its clearing arrangements, like a brokerage account |
| Fee model | Taker fee per market: C × rate × p × (1 − p); makers pay no platform fee | Taker fee: rounded up 0.07 × C × P × (1 − P); maker fees on some series only |
| How questions settle | UMA's optimistic oracle, with disputes and token-holder votes (see how markets resolve) | The exchange determines outcomes from the source named in each contract's rules |
| Market count | About 2,100 active events on 2026-11-07 (Gamma API) | Check Kalshi's site |
| API and data access | Public, no key needed for reading: Gamma API (markets), CLOB API and WebSocket (prices, books), Data API (trades, holders); wallet positions are public on-chain | Public API with market data endpoints and a WebSocket; trading requires an account and API keys |
Which one can I use in my country?
It depends on where you live, and both lists change.
- Polymarket's international platform lists the United States, the United Kingdom, France and about 35 other countries and regions as close-only (you can close positions, not open new ones) and blocks sanctioned places completely. Nimb checks Polymarket's geoblock endpoint before every order and will not let a blocked location open a position. See eligibility and restricted countries. Do not use a VPN to get round it.
- Polymarket US is a separate, CFTC-regulated venue for US users. The CFTC approved an amended order of designation in November 2025 allowing intermediated US access. Nimb does not map it.
- Kalshi is available to US residents, though some US states dispute its sports contracts in court, and it opened to users in many other countries from October 2025.
Earlier history matters for context: in January 2022 the CFTC fined Polymarket's operator $1.4M for offering event-based binary options without being a designated contract market, and ordered it to wind down the markets that did not comply (CFTC release 8478-22). Its international platform has blocked US users since then.
What does regulation change for you?
Mostly three things: where your money sits, who settles disputes, and who you can complain to.
- Custody. On Kalshi, your dollars and positions sit in an account at a regulated exchange, as at a broker. On Polymarket's international platform, pUSD and shares sit in a wallet you control: nobody can freeze it, and nobody can recover it if you lose your recovery phrase.
- Settlement. Kalshi decides outcomes under rules it files with the CFTC. Polymarket relies on UMA's oracle, which is open to anyone to dispute but ends, in the hardest cases, in a token-holder vote.
- Recourse. A CFTC-regulated venue has rules on surveillance, market supervision and customer complaints. A crypto venue offers transparency instead: every trade and position is visible on-chain.
Neither model removes the main risk, which is the same on both: you can lose your whole stake if the outcome goes against you.
How do their fees compare?
Both venues use the same shape of taker fee: proportional to p × (1 − p), so it is largest at 50% and falls toward 0 near 0% and 100%. What differs is the multiplier and where it applies.
| Price | Kalshi (0.07) | Polymarket (0.04) | Polymarket (0) |
|---|---|---|---|
| 10% | $0.63 | $0.36 | $0.00 |
| 30% | $1.47 | $0.84 | $0.00 |
| 50% | $1.75 | $1.00 | $0.00 |
| 90% | $0.63 | $0.36 | $0.00 |
Taker fee on 100 contracts (Kalshi) or 100 shares (Polymarket); illustrative arithmetic from the published formulas. On Polymarket the rate is set per market, so read it from the market rather than assuming a category; 0.04 and 0 are rates seen on Politics and Geopolitics markets in Nimb's data on 2026-11-07. Makers, whose resting orders are filled by others, pay no Polymarket platform fee. Spreads, which you pay on both venues, often cost more than the fee.
Nimb's own fee is separate. Nimb earns a small builder fee on Polymarket orders placed through Nimb, included in the price you see. Nimb earns nothing from Kalshi and has no commercial relationship with it. More in fees and all-in pricing and independence and business model.
Which has more markets and liquidity?
Both venues cover politics, economics, sport, crypto, culture and weather; the mix differs. Polymarket has more geopolitics and crypto markets and trades around the clock with a global trader base. Kalshi, as a US-regulated exchange, has strong coverage of US economic data, rates, weather and sport. Liquidity is concentrated on both: a small number of headline markets carry most of the money, and many listed markets have thin books. Compare a market's spread and depth, not the venue's total volume.
Do prices differ for the same event?
Often, by a few points, and sometimes by more. Reasons:
- The questions are not identical. A different resolution source, deadline or time zone makes them different contracts. Read both rules before comparing prices.
- Different traders. Each venue's price reflects the people who can and do use it.
- Hard to arbitrage. Moving money between a dollar account and a crypto wallet, different fees and eligibility rules mean gaps can persist.
- Different settlement. A price on Polymarket also carries the risk of an oracle dispute; on Kalshi, the exchange's own determination.
Researchers studying the 2024 US presidential election found that daily price moves for the same outcome were only weakly related across PredictIt, Kalshi and Polymarket (Clinton and Huang, SocArXiv working paper, 2025). When two venues disagree, the gap is itself a reading: it tells you how uncertain the price is.
Which does Nimb show and why?
Nimb maps Polymarket's international platform. Its data is public and open to anyone without a key, from market lists to order books to the wallets that hold each side, which is what the map needs: holders and wallet lines are only possible because Polymarket's positions are on-chain. Orders placed through Nimb go to Polymarket from the wallet you connect; Nimb never holds funds.
Nimb does not show Kalshi prices, so it cannot show the gap between the two venues for the same event. More on how Nimb works on about Nimb.
Prediction markets are risky; you can lose your whole stake on either venue. Nothing here is financial advice or a recommendation of one venue over the other.
Last reviewed 2026-11-07 · Data from Polymarket · Not financial advice · Nimb is not affiliated with Polymarket.