NASDAQ ITCH

Nasdaq ITCH is the direct data feed protocol providing individual message tracking for every event in the Nasdaq execution system.

Nasdaq TotalView-ITCH delivers the full order book depth for the Nasdaq market center. It uses a high-performance binary protocol to transmit every quote and order (from entry to execution or cancellation) with nanosecond-level timestamps. By bypassing the slower SIP (Securities Information Processor) consolidation process, ITCH provides traders with the raw data necessary to view the complete market liquidity at every price level. It is the gold standard for high-frequency trading firms and institutional desks requiring sub-millisecond transparency into the exchange's matching engine.

https://www.nasdaqtrader.com/Trader.aspx?id=ITCH