A dark pool is a trading venue that does not publicly display its orders before execution. Buyers and sellers can seek matches without revealing the full size and price of their interest in a visible order book.
Why hide an order?
A large publicly displayed order can alert other traders and move prices against its owner. A dark pool aims to reduce this information leakage. Depending on the venue, matching may use prices derived from public markets or other disclosed pricing rules. A match still requires compatible trading interest; confidentiality does not guarantee liquidity or a better price.
The term originated in securities markets and is also used for crypto trading systems with limited pre-trade transparency. Their custody, settlement and access arrangements can differ substantially.
What “dark” does not mean
Dark pools are not automatically unregulated or permanently secret. For example, US securities dark pools have trade-reporting obligations. Those requirements should not be assumed to apply identically to every crypto venue.
Reduced visibility can make execution quality and conflicts of interest harder to assess. A dark pool is also different from a privacy coin: hiding an order before execution does not necessarily hide a later blockchain transfer.