Market Data

Contracts, quotes, order books, and trades

Market data is delivered over WebSocket streams — see each section below for the specific stream — with a small REST surface for discovery via the Get Expirations and Get Contracts endpoints.

Contracts

A contract is a single tradable option, identified by its contract name. Each contract publishes:

Field	Description
markPrice / bidPrice / askPrice	Mark, best-bid, and best-ask prices
markIV / bidIV / askIV	Implied volatility per side (see Pricing & Greeks)
delta / gamma / vega / theta / rho	Greeks
forward	Forward price
openInterest	Total open contracts
volume24h	24-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 Get Expirations and Get Contracts REST endpoints.

Each expiry also carries an expectedPriceMove, with the atmIV and indexPrice behind it — see Expected Price Move.

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 top of book.

Order Book

The Order Book Stream provides the full book for a single contract as a snapshot followed by delta updates. 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

Price	Where it comes from	Used for
Index price	Underlying spot index	Margin, settlement reference
Mark price	Black-76 fair value from mark IV	Margin, unrealized PnL
Forward price	Expected underlying price at expiry	Black-76 pricing input
Settlement price	Underlying price at expiry (08:00 UTC)	Settlement payoff