Perps API

The Perps API is how you trade Kalshi’s perpetual futures. “Perps”, “margin”, and “perpetual futures” all refer to the same product. The API surface uses margin throughout (endpoints under the /margin namespace, margin-prefixed fields), so these docs use margin for technical references. It mirrors the existing event contract API, so if you’re already integrated there you’re most of the way there: the margin endpoints follow the same patterns, authentication, and conventions, just under /margin.

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Connectivity

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REST API

Use the external-api hosts for perps REST. WebSocket and FIX use the separate perps hosts listed below.

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WebSocket API

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FIX API

The margin FIX gateway uses a separate host from event contract FIX. Available session types:

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API Reference

The Perps API mirrors the event contract API (same auth, pagination, error format, and order lifecycle), so the conventions in Making Your First Request and API Environments apply directly.

• REST: see the REST reference in this section.
• WebSocket: see the margin channels under WebSockets in this section.
• FIX:
  • Connectivity
  • Authentication & Sessions
  • Order Entry
  • Order Groups
  • Market Data
  • Drop Copy
  • Listener Sessions
  • Error Handling

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REST API

What’s the same: authentication, pagination, error format, and core order lifecycle (create, amend, decrease, cancel) all work identically, just under /margin/* instead of /portfolio/* and /markets/*. Margin-specific additions: beyond the mirrored order, market, and order-group endpoints, margin adds endpoints for account balance and risk, funding (estimated and historical rates, plus payment history), fee tiers, subaccounts, and transfers between your event-contract and margin balances. See the REST reference for the full list. Two things to know up front: the event-contract ↔ margin transfer (/portfolio/intra_exchange_instance_transfer) is not yet available (enabled with the production rollout), and you can call /margin/enabled to check whether margin is on for your account in a given environment. Not available on margin:

• Batch order operations (BatchCreateOrders, BatchCancelOrders)
• Queue positions
• Events, series, milestones, multivariate collections, structured targets
• RFQs and quotes
• Historical data endpoints
• Exchange schedule

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WebSocket API

Same channels: orderbook_delta, ticker, trade, fill, user_orders, order_group_updates Not available on margin: market_positions, market_lifecycle_v2, multivariate_market_lifecycle, multivariate, communications Timestamp convention: all timestamp fields in margin WebSocket payloads use Unix epoch milliseconds and an _ms suffix.

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FIX API

What’s the same: FIXT.1.1 / FIX50SP2 protocol, RSA key authentication, order lifecycle messages (NewOrderSingle, OrderCancelRequest, etc.), order groups, drop copy, and listener sessions all work the same way. Key differences: