Kalshi and Polymarket data shapes

Kalshi and Polymarket data shapes

A neutral guide to Kalshi and Polymarket data. It covers venues, event contracts, and cross-platform market data.

Identifiers and market records

Adjacent prefixes Kalshi ids, such as kalshi:GOVPARTYAL-26-R. Polymarket records use slugs. A trailing machine-id digit run may show in the title. The page strips that run. The full value stays available.

Quotes and price history

Market detail can include yes_bid and yes_ask, plus derived No-side values. Candle rows can be marked synthetic_book. Polymarket price-history candles lack a bid and ask pair.

A neutral integration checklist

Keep the platform-prefixed id and the venue. Treat order books and candles as different shapes. Use the supplied event and settlement metadata. Do not assume the venues resolve contracts the same way.

Terms used on this page

Event contract
A contract whose value follows a defined event, such as an election. It settles on the outcome. It does not trade a continuous price forever.
Prediction market
A venue where event contracts trade, so their prices express a market-implied probability of the event happening.
Prediction market index
A rules-based benchmark built from selected event contracts. An index provider calculates it, not a venue.

Sources

Page last reviewed: 2026-09-24.