What Is a Dark Pool? How to Read Dark Pool Data

Roughly 40–50% of US stock volume happens in "dark pools" every day. They are not a black market — they are institutions' off-exchange block venues. Understanding them reveals the other side of the money.

What is a dark pool?

A dark pool is an off-exchange venue: large institutional orders are matched internally instead of on the public book, so big trades don't move the price. After execution, trades are disclosed as "prints" — which is how we can see them.

Dark pool vs the lit market

• Lit market — public exchange matching, tick by tick, a price everyone can see.
• Dark pool — off-exchange blocks (ATS / TRF), large, disclosed after execution.
• They are two sides of the same money — read one alone and you'll misread it.

How to read dark pool data

• Dark pool net buy/sell — is the day net buying or selling, and how big?
• Compare with the lit market — lit buying + dark selling often signals distribution; lit selling + dark buying often signals absorption.
• Combine with short volume — heavy off-exchange shorting often means hedging or bearish pressure.

Common mistakes

• Treating dark pools as "insider" — they are public, disclosed off-exchange data.
• Looking at a single day's dark volume without its relation to price and the lit market.
• Confusing dark pools with pre-market / after-hours trading.