To compare a Kalshi contract with a Polymarket one you first have to know what each platform calls an event and a market, because the words do not line up exactly. This article summarises how Kalshi's documentation describes its objects and tickers, and what that means for matching. It is not trading advice, and the details can change, so check the current documentation.
Three levels
Kalshi's glossary defines a market as a single binary market, an event as a collection of markets and the basic unit members should interact with, and a series as a collection of related events. The documentation says events in a series look at similar data for determination over disjoint time periods, should have no logical outcome dependency between them and share a ticker prefix. Each event belongs to exactly one series (series_ticker) and each market to exactly one event (event_ticker).
An example from the documentation
The documentation's example is a monthly US gas price series. The series ticker is KXAAAGASM, an event is KXAAAGASM-26SEP30 (one per month) and a market is KXAAAGASM-26SEP30-3.00 (one per price strike). Categories and tags are fields on the series used for discovery; they are not levels above it and are not part of the ticker convention.
Do not parse tickers
The documentation says tickers often follow the Series, Event, Market pattern but with occasional exceptions, and tells developers not to infer relationships from the strings. Use the series, event, market and search endpoints and the fields they return instead.
Why it matters when pairing with Polymarket
Polymarket also has events and markets, and an event can contain several markets (see the negative risk article). A pair is only meaningful when you compare the same level: one Kalshi market (one strike, one outcome) against the one Polymarket market that asks the same question with the same resolution rules. Matching a whole event to a single market, or two strikes that differ, is a way to build a pair that looks aligned and is not. The checklist in UMA disputes and resolution mismatch applies once the levels line up.
Where Arbitrage Agent fits
Arbitrage Agent matches markets across Kalshi and Polymarket, checks the resolution rules on both sides, and shows the result in a live feed with a step-by-step guide for both legs. You place the orders yourself, and the final check of the details is still yours. See the plans or start with the Starter plan.
Related articles
- Polymarket UMA Disputes and Resolution Mismatch
- Kalshi API Guide
- Event Contracts Explained
- Kalshi Market Lifecycle and Statuses
Key terms: Event Contract · Resolution Risk