Depth from an ECN: what it shows and what it hides
Posted: Sat Oct 31, 2026 9:16 pm
Some brokers offer ECN accounts with a view of the aggregated order book. Traders see bid and ask sizes at several price levels.
It looks like real order flow, and it carries some information: where liquidity sits, how thin the book is, how quickly levels vanish.
But the book reflects only the participants connected to that broker's pool. Large banks and funds trade in venues retail cannot see. And orders in the book can disappear in an instant, as liquidity providers update quotes thousands of times a second.
Another risk is reading too much into it. A big order at a level may be real, or it may be bait that vanishes when price approaches.
For scalpers, depth is most useful as a measure of thinness. A book with small sizes means a larger order will move price, and slippage is likely.
The best use is as context, not as a trigger.
Has depth data been useful in practice, and how was it validated?
It looks like real order flow, and it carries some information: where liquidity sits, how thin the book is, how quickly levels vanish.
But the book reflects only the participants connected to that broker's pool. Large banks and funds trade in venues retail cannot see. And orders in the book can disappear in an instant, as liquidity providers update quotes thousands of times a second.
Another risk is reading too much into it. A big order at a level may be real, or it may be bait that vanishes when price approaches.
For scalpers, depth is most useful as a measure of thinness. A book with small sizes means a larger order will move price, and slippage is likely.
The best use is as context, not as a trigger.
Has depth data been useful in practice, and how was it validated?