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Market Data

Market Data

Prediction Markets market data is organized around events and their contracts. Use the public REST API to discover the markets that are currently available and to resolve each contract to its instrumentSymbol. Use REST for discovery and snapshots, then use WebSocket streams for low-latency updates.

Market-data workflow

1. List active events and choose an event.
2. Get the event details using the event ticker.
3. Identify a contract and save its instrumentSymbol.
4. Read the event snapshot for the contract’s current pricing and order-book fields.
5. Subscribe to WebSocket streams for continuing updates.

List active events

Use List Events with status=active to discover events that are currently active. The response is paginated; use limit and offset to retrieve additional results. You can also filter by category or search the event title with search.

Code
curl "https://api.gemini.com/v1/prediction-markets/events?status=active&limit=50"

Each event includes an event ticker, such as FEDJAN26, along with its title, status, expiry, and contracts. Keep the event ticker for the next request. Do not construct a contract symbol from the title or slug: use the instrumentSymbol returned for the contract.

Get event details

Call Get Event with the event ticker:

Code
curl "https://api.gemini.com/v1/prediction-markets/events/FEDJAN26"

The event response provides the authoritative event definition and its contracts array. It can also include contract pricing and contractOrderbooks. Treat the event and contract status values as metadata, and verify that the contract is still available before using it for a live subscription.

For crypto Up/Down events, the Get Strike Price for Event endpoint provides strike information when it becomes available.

Identify a contract

Select a contract from the event’s contracts array. The fields most useful for market-data clients are:

Field	Use
ticker	Contract-level identifier returned by the event API.
label	Human-readable outcome, such as Yes or No.
status	Contract lifecycle status.
marketState	Whether the contract is currently open or closed for trading.
instrumentSymbol	Symbol required by the REST market-data routes and WebSocket stream names.
prices	Current contract pricing, including bestBid, bestAsk, and lastTradePrice when available.

For example, a contract may return:

Code
{
  "ticker": "FEDJAN26-DN25",
  "label": "Fed cuts at least 25 bps",
  "status": "active",
  "marketState": "open",
  "instrumentSymbol": "GEMI-FEDJAN26-DN25"
}

Use the exact instrumentSymbol value, including capitalization and punctuation, in subsequent requests. The instrument identifies the contract's proposition in YES space. Orders select the yes or no outcome separately; do not append an outcome to the symbol unless Gemini returned it as part of the symbol.

Read the event snapshot

The Prediction Markets event response is the REST discovery snapshot. Its contract records can include current prices and contractOrderbooks fields, alongside the contract status and instrumentSymbol. Use those fields for discovery and initial display, then use the Prediction Markets WebSocket streams for live book and trade updates.

Prices and quantities are returned as strings. Preserve that precision instead of converting values to binary floating-point numbers. After a disconnect or a missed update, request the event again and resubscribe before resuming local state.

Subscribe to WebSocket streams

Connect to wss://ws.gemini.com and subscribe using the contract’s instrumentSymbol. The Prediction Markets WebSocket introduction documents the connection, and the Stream Reference documents payloads and stream names.

Choose a stream based on the data you need:

Stream	Use
{instrumentSymbol}@bookTicker	Real-time best bid and ask.
{instrumentSymbol}@depth5, @depth10, or @depth20	Periodic top-of-book snapshots.
{instrumentSymbol}@depth or @depth@100ms	Differential depth updates for maintaining a local order book.
{instrumentSymbol}@trade	Real-time executions.

For a differential depth stream, connect with snapshot=-1 to receive a full initial order-book snapshot, then apply subsequent updates. Public depth is normalized in YES space; derive NO notional with 1 - yesPrice. If update IDs skip ahead, discard the local book and resubscribe to resynchronize. The stream reference also explains how zero quantities remove price levels.

WebSocket subscriptions use the symbol returned by the event API. For example, a subscription name for the contract above is:

Code
GEMI-FEDJAN26-DN25@bookTicker

Use WebSocket as the primary source for active monitoring and trading workflows. Keep the REST event and market-data endpoints available for discovery, initialization, reconnect recovery, and audit snapshots.