Polygon.io

Polygon.io (now known as Massive) provides institutional-grade real-time and historical market data directly from major exchanges such as NYSE, Nasdaq, and Cboe. Built for developers, builders, and financial innovators, the platform offers multiple flexible data delivery methods (RESTful APIs, WebSocket, SQL, and flat files) with direct connectivity for low-latency, accurate, and reliable access. Its intuitive platform is designed to support applications ranging from trading apps to robo-advisors, making robust financial data accessible to both enterprises and individuals.