Dome API alternatives for Kalshi and Polymarket

Dome unified Polymarket and Kalshi data. Polymarket acquired it in February 2026; Dome's docs say all APIs reached end of life on 28 April 2026 and recommend Polymarket's own APIs.

Decision

Choose Narwhal to keep both venues in one schema for economics, central banks, metals and energy. Use direct exchange APIs for wider market coverage, Tatum for another shared interface, or specialist services for historical research and sports.

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Provider shortlist

Dome is retired and is not ranked among the replacement options. Narwhal API is owned and operated by Nusantara Ventures, LLC.

Kalshi API

Moving Kalshi workloads to the exchange's own data API.

Polymarket API

Following Dome's recommendation to use Polymarket's own APIs.

Tatum

Retaining one key and base URL for both venues.

PolymarketData

Rebuilding historical Polymarket analysis with snapshots and file exports.

Odds-API.io

Sports prediction prices alongside existing sportsbook data.

Compare the options

Best fit is not feature parity. Check the evidence and limitation together.

ProviderBest forEvidence checkedImportant limitation
Narwhal APIReplacing a shared venue interface for economic and commodity odds.Kalshi and Polymarket odds share one schema, REST and MCP; Basic and Pro add WebSocket streaming.Free returns the previous day's close; coverage excludes sports, politics and crypto markets.
Kalshi APIMoving Kalshi workloads to the exchange's own data API.Public REST data needs no key; official SDKs cover Python and TypeScript.Kalshi only; WebSocket requires authentication, and historical retention is not stated.
Polymarket APIFollowing Dome's recommendation to use Polymarket's own APIs.Three REST hosts cover discovery, prices and activity; a public market WebSocket channel is available.It does not replace Kalshi coverage; Gamma encodes outcome labels, prices and token IDs as JSON strings.
TatumRetaining one key and base URL for both venues.It lists 24 Polymarket and 14 Kalshi endpoints, plus hourly and daily OHLCV candles.Prediction endpoint pricing and WebSocket support are unpublished; prediction tools through its MCP server are unconfirmed.
PolymarketDataRebuilding historical Polymarket analysis with snapshots and file exports.It lists 1-minute history from August 2025, L2 snapshots, a Python SDK and S3 dumps.It is independent of Polymarket and covers no Kalshi data.
OddsPapiReplacing sports-market feeds alongside bookmaker odds.The WebSocket-first aggregator lists Kalshi and Polymarket among 350+ bookmakers.Its guides cover sports only; free quota is small and paid plans have custom prices.
Odds-API.ioSports prediction prices alongside existing sportsbook data.Kalshi and Polymarket are supported bookmakers; Solo costs $65/month, with 5,000 requests an hour on paid plans.Sports only; new free keys are paused indefinitely, and no official MCP server is established here.

Choose by requirement

Keep both venues connected

Narwhal serves both venues under one key for supported economic and commodity topics. Direct Kalshi and Polymarket integrations require separate response mapping.

Check the replacement scope

Tatum lists both venues; PolymarketData covers Polymarket history only. OddsPapi and Odds-API.io cover sports, which Narwhal does not.

Plan for data differences

Review event identifiers, outcome shapes and timestamps before migrating. Narwhal provides scalar, binary, extremes and timing shapes, with an official resolution source on each event.

Sources and review date

Each detailed provider page lists the first-party documentation used, its evidence boundaries, and its review date.

Reviewed:

Test the overlapping job

Inspect Narwhal's published coverage and response contract before choosing a provider.

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