A broad variety of providers offer market data for various asset classes. Examples in relevant categories include:

• Exchanges derive a growing share of their revenues from an ever broader range of data services, typically using subscription.
• Bloomberg and Thomson Reuters have long been the leading data aggregators with a combined share of over 55% in the $28.5 billion financial data market. Smaller rivals, such as FactSet, are growing, or emerging, such as money.net and Quandl as well as Trading Economics or Barchart.
• Specialist data providers abound. One example is LOBSTER, which aggregates Nasdaq order-book data in real-time.
• Free data providers include Alpha Vantage that offers Python APIs for real-time equity, FX, and crypto-currency market data, as well as technical indicators.
• Crowd-sourced investment firms that provide research platforms with data access include, in addition to Quantopian, the Alpha Trading Labs, launched in March 2018, which provide HFT infrastructure and data.