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Endpoints

Order Entry Host: margin-mm.fix.elections.kalshi.comMarket Data Host: margin-marketdata.fix.elections.kalshi.com
PurposePortTargetCompIDDescription
Order Entry (without retransmission)8228KalshiNRSubmit, modify, and cancel orders; no message persistence or retransmission. Supports Listener Sessions for read-only streaming
Order Entry (with retransmission)8230KalshiRTOrder entry with message retransmission. Supports Listener Sessions for read-only streaming. Contact institutional@kalshi.com for access
Drop Copy8229KalshiDCRequest-response queries for historical execution reports
Market Data8233KalshiMDOrder book snapshots and incremental updates. Available only on market data host

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Session Configuration

All connections use FIXT.1.1 with application version FIX50SP2.
ParameterValue
SenderCompIDYour FIX API key (UUID format)
TargetCompIDOne of KalshiNR, KalshiRT, KalshiDC, or KalshiMD
Session IDTargetCompID + SenderCompID
Only one FIX connection is allowed per API key. Separate API keys are required for concurrent connections.

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SSL/TLS

You must use TLS 1.2 or higher (not plain TCP) to connect to the margin FIX gateway. Cipher suites follow AWS Network Load Balancer TLS policies. If your FIX implementation does not support native TLS connections, use a local proxy such as stunnel. To obtain the server certificate for pinning on the initiator side: 
openssl s_client -showcerts -connect <host>:<port> < /dev/null | openssl x509 > kalshi-fix.pem

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Private Connectivity

For participants requiring network-level isolation, Kalshi supports private connectivity via AWS PrivateLink. With PrivateLink, FIX traffic is routed entirely within the AWS backbone and never traverses the public internet. Contact institutional@kalshi.com to provision a PrivateLink endpoint for your AWS account.

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Rate Limits

  • Limit: FIX application messages use the same token model, token costs, and margin Read/Write buckets as the equivalent REST API operations.
  • Scope: Application messages only (from client to server)
  • Excluded: Logout (35=5), Heartbeat (35=0), TestRequest (35=1)
  • Logon (35=A) is rate-limited.
  • Order-entry messages use the margin Write bucket. See Rate Limits and Tiers for tier budgets and token-cost behavior.
  • Mass Cancel Request (35=q) is limited to 1 request/second.

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Maintenance Window

See Maintenance and Pauses for scheduled maintenance times and the difference between trading pauses and exchange pauses. Sessions may be disconnected during the maintenance window. Kalshi does not initiate sequence number resets during maintenance; clients should reset sequence numbers on their side when reconnecting. KalshiRT sessions retain message continuity across the maintenance window. If your KalshiRT session is disconnected, you can request retransmission of any messages missed during the downtime after reconnecting.

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CancelOrderOnPause

To control what happens to your resting orders during a pause, set tag 21006 (CancelOrderOnPause) on your New Order Single (35=D) messages:
ValueBehavior
YOrder is automatically cancelled when a trading or exchange pause begins
N (default)Order remains resting on the book and resumes when activity reopens