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Market data is delivered over the WebSocket, with a small REST surface for discovery. This guide explains what’s available and where to get it.

Contracts

A contract is a single tradable option, identified by its contract name. Each contract publishes:
FieldDescription
markPrice / bidPrice / askPriceMark, best-bid, and best-ask prices
markIV / bidIV / askIVImplied volatility per side (see Pricing & Greeks)
delta / gamma / vega / theta / rhoGreeks
indexPriceUnderlying index price
openInterestTotal open contracts
volume24h24-hour traded volume
Contracts are scoped by underlying and expiration date. Stream what’s tradable live on the Contracts Stream, or list them with the REST Get Expirations and Get Contracts endpoints.

Quotes

The Quotes Stream delivers top-of-book best bid/ask (with size and IV) for each contract — a lighter feed than full contracts when you only need the current market.

Order Book

The Order Book Stream provides the full book for a single contract as a snapshot followed by delta updates, with per-level implied volatility. Apply deltas in order to maintain a local book.

Trades

The Public Trades Stream provides real-time executions for a contract, and a snapshot of recent trades on request.

Prices Used Across the API

PriceWhere it comes fromUsed for
Index priceUnderlying spot indexMargin, settlement reference
Mark priceBlack-76 fair value from mark IVMargin, unrealized PnL
ForwardExpected underlying price at expiryBlack-76 pricing input
Settlement priceUnderlying price at expiry (08:00 UTC)Settlement payoff