fastest financial data api

If you mean lowest-latency / fastest market data API, the answer depends on what kind of “financial data” you need:

Fastest options by use case

• Real-time equities / options / crypto tick data:
  Polygon.io, Twelve Data, Intrinio, Tradier (varies by asset class and plan)
• Institutional-grade ultra-low latency / direct feeds:
  Bloomberg B-PIPE, LSEG Refinitiv, ICE Data, exchange-native feeds
• Crypto specifically:
  Coinbase Advanced Trade API, Binance API, Kraken API
  (exchange-native APIs are often fastest for their own venue)
• Historical + moderately fast real-time:
  Alpha Vantage, Finnhub, Tiingo, IEX Cloud
  (good APIs, but usually not the absolute fastest)

If your priority is speed

Choose based on:

1. WebSocket support for streaming
2. Venue-native data if possible
3. Proximity/region to the exchange
4. Rate limits and throttling
5. SLA / latency guarantees

Practical recommendation

• Best general-purpose fast API: Polygon.io
• Best for crypto speed: exchange-native APIs like Binance or Coinbase
• Best institutional feed: Bloomberg B-PIPE or Refinitiv

If you tell me:

• asset class (stocks, crypto, forex, options)
• real-time or historical
• budget

…I can recommend the single fastest/best API for your case.