Alpaca
Alpaca (AlpacaDB, Inc.) · Financial analysis & investing
API-first US brokerage offering a Trading API, Market Data API and Broker API for stocks, ETFs, options and crypto, with paper trading
Apache-2.0FreemiumUsage-basedNov 2, 2026
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Kraken API
Payward, Inc. (Kraken) · Financial analysis & investing
REST, WebSocket and FIX interfaces to the Kraken cryptocurrency exchange for market data, spot and derivatives trading and account management
ProprietaryFreeUsage-basedNov 2, 2026
Massive (formerly Polygon.io)
Massive (Polygon.io, Inc.) · Market & fundamentals data
Market data platform (renamed from Polygon.io in October 2025) with REST and WebSocket APIs, flat files and SQL access for US stocks, options, indices, forex, crypto and futures
ProprietaryPaidEnterpriseNov 2, 2026
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