Kalshi vs Polymarket: Record $19bn Week Widens Kalshi's Lead as Legal Fights Spread

Prediction markets have set a weekly volume record four weeks in a row, with an estimated $23.9 billion traded across the sector in the week ending 11 October, according to figures compiled by CryptoRank. Daily figures from DeFi Rate show Kalshi came within touching distance of $4 billion in a single session.

Both platforms let customers buy "yes" or "no" contracts on real-world events, and both are regulated at federal level by the Commodity Futures Trading Commission (CFTC). The headline volumes are not directly comparable, however: Kalshi counts each contract at its $1 face value, while Polymarket figures can be quoted either as contracts or as cash traded.

Sports Parlays Drive Kalshi's Lead

Sports explain most of the gap. Sports contracts make up roughly two thirds of Kalshi's volume, and parlays, which combine several outcomes in a single contract, have become the engine of its record days, Crypto Briefing reported.

Polymarket's US app is growing faster from a smaller base. Its strength remains politics, economics and world events, and the US midterm elections on 3 November will be its next major test.

There are warning signs in the numbers too. CNBC reported in late September that unusually uniform trade sizes made up a large share of volume in some Kalshi crypto products, a reminder that headline volumes are not audited figures.

Who Runs Kalshi

Kalshi was founded in 2018 by chief executive Tarek Mansour and Luana Lopes Lara, and in 2020 became the first company to win CFTC approval as a designated contract market built around event contracts, which is why it has always operated legally for US users at federal level.

It raised $1 billion at a $22 billion valuation in May 2026 in a round led by Coatue, and Bloomberg reported at the end of September that it was in final talks for a new round at roughly $40 billion. Mansour has said a stock market listing is possible but has ruled out a 2026 debut.

What Is Polymarket and Who Owns It

Polymarket is a prediction market founded in 2020 by Shayne Coplan, who still runs it. It built its name on election and world-event markets settled in USDC, a dollar stablecoin.

After a 2022 settlement with the CFTC it blocked American users from its main site, then returned by a different route. In July 2025 it bought QCEX, a CFTC-licensed exchange and clearing house, for $112 million, and in November 2025 the regulator approved an intermediated US platform on which customers trade through registered brokers. The waitlist for the US app was removed in May 2026, while the international site remains closed to US users.

Its largest strategic investor is Intercontinental Exchange, owner of the New York Stock Exchange, which committed up to $2 billion in October 2025 and had built a stake of about $1.64 billion by March 2026, according to Bloomberg. Polymarket was reported in August to be in early talks to raise about $1 billion at a valuation above $20 billion, although no closing had been announced at the time of writing.

Kalshi and Polymarket Fees

Both platforms charge a fee on trades that take liquidity, and on both the fee peaks when a contract trades near 50 cents. Kalshi's widely reported taker formula is 0.07 multiplied by the number of contracts, the price and one minus the price, which works out at about $1.75 per 100 contracts at 50 cents. Resting limit orders pay less, or nothing, depending on the market.

Polymarket US launched with a near-zero fee and has raised it in steps. Several trackers report a taker formula of 0.06 on the same basis since 1 July 2026, or about $1.50 per 100 contracts at 50 cents, with a rebate paid to market makers. Fee schedules on both platforms change often.

Is Kalshi Legal, and Is Polymarket Legal in the US?

At federal level, yes. The CFTC treats event contracts as swaps rather than gambling, and that position is now being contested state by state.

The Third Circuit sided with Kalshi against New Jersey in April. The Ninth Circuit ruled against it in Nevada in August, and the Sixth Circuit ruled against it 3-0 in the Ohio and Tennessee cases on 25 September, deepening the split between the appeals courts. Kalshi asked the Sixth Circuit for a rehearing on 9 October.

The CFTC has gone on the offensive, suing Wisconsin in April and going to court against Kentucky, and it sent two new prediction market rules to the White House for review on 28 September. Among the states, Massachusetts ordered platforms to block residents in February and Polymarket countersued, while Minnesota's first state ban on prediction markets was blocked by a federal court on 27 July. New York has sued both companies, and in Maryland Kalshi is live while Polymarket's sports markets are held up by litigation, according to CBS Sports' state tracker.

Kalshi has also failed in its bid to block enforcement of Iowa's gambling law, and outside the US the Czech Republic has ordered internet providers to block the platform.

Is Kalshi Legal in California?

Kalshi operates in California, but its sports contracts face a growing legal risk there. On 16 September the Ninth Circuit found that two California tribes, Blue Lake Rancheria and Chicken Ranch Rancheria, are likely to win their claim that Kalshi's sports contracts on their lands breach the Indian Gaming Regulatory Act.

The ruling is preliminary rather than final, and Kalshi has asked the full court to rehear it. Polymarket also operates in California under its federal licence, and the tribal cases filed so far name Kalshi. Tribal nations have separately urged the Supreme Court to review the wider dispute.

What Comes Next

New Jersey has asked the US Supreme Court to settle the question. With the circuits split, the Supreme Court is the likely final word on whether states can treat sports event contracts as gambling. In the meantime, the CFTC's new rules, now under White House review, could settle how sports contracts and promotions are handled at federal level.

Overseas, the UK's Financial Conduct Authority confirmed on 6 October that it is in talks with prediction market operators about possible entry, although its ban on selling binary options to retail customers still applies to the products it has examined. For British bookmakers and betting exchanges, the US boom is already a competitor, even if in Britain it is not yet a product.