Reading the depth window on a raw ECN account
Posted: Tue Oct 27, 2026 5:06 am
Some ECN accounts show a depth of market panel with several price levels. It looks like a window into the real order book. It isn't quite that.
What it shows is aggregated liquidity from the broker's providers, not the whole market. Size at each level is what is available through that broker, and it can change in milliseconds. Large displayed size can vanish when an order hits, a phenomenon familiar to anyone who has tried to trade against a big bid.
Still, there's usable information. Thin depth near the touch warns about slippage on larger orders. Sudden depth removal on one side sometimes comes just before a quick move. And watching how fast levels refill hints at how liquid the moment really is.
A small experiment: open the depth panel, watch one pair for ten minutes during a calm period and ten minutes during the London open, and just note what changes. Number of levels, size at the best price, how quickly gaps in the book fill. Most people find the contrast surprisingly large, and it says plenty about when a larger order can be executed cleanly and when it can't.
Do depth panels actually change decisions for anyone here, or do they end up as decoration on the screen? And what behaviors in the book seem to matter?
What it shows is aggregated liquidity from the broker's providers, not the whole market. Size at each level is what is available through that broker, and it can change in milliseconds. Large displayed size can vanish when an order hits, a phenomenon familiar to anyone who has tried to trade against a big bid.
Still, there's usable information. Thin depth near the touch warns about slippage on larger orders. Sudden depth removal on one side sometimes comes just before a quick move. And watching how fast levels refill hints at how liquid the moment really is.
A small experiment: open the depth panel, watch one pair for ten minutes during a calm period and ten minutes during the London open, and just note what changes. Number of levels, size at the best price, how quickly gaps in the book fill. Most people find the contrast surprisingly large, and it says plenty about when a larger order can be executed cleanly and when it can't.
Do depth panels actually change decisions for anyone here, or do they end up as decoration on the screen? And what behaviors in the book seem to matter?