Polymarket US launches API beta for sports parlay contracts

Polymarket US has launched an API-only beta for multi-leg sports contracts, known as parlays, which began processing trades on August 5. The product, officially called the Combinatoric Athletic Outcome Contract, allows for bets involving between two and 10 legs. For a contract to pay out, every individual leg must be successful; if any single leg loses, the entire contract pays nothing.

Data indicates that the beta has seen 16,173 trades, generating $7.4 million in volume and approximately $928,093 in stakes. This rollout follows Polymarket US certifying the product with federal regulators in May and amending terms in July. Notably, the parlay option is currently restricted to approved API users and does not appear in the exchange’s consumer app or desktop site.

The move comes as competitor Kalshi has seen significant activity in the parlay market. Kalshi reportedly collected approximately $25 million in parlay taker fees during the first 16 days of August. While there have been unverified reports regarding Kalshi adding maker fees to its parlay products, its official published fee schedule does not currently list any such changes.