Quote flow
Also called NBBO quote pressure, quote pressure
Quote flow is cumulative bid and ask quote size at each price, showing where resting liquidity actually sits rather than where trades printed.
In more detail
Most order-flow tools measure trades: what executed, at what price, in what size. Quote flow measures the other half of the book — how much size is being quoted at each price and how that changes second by second.
It answers a different question. Trade prints tell you what happened; quote size tells you what is standing there now, and where liquidity is thinning or building before price gets there.
How Hermes measures it
Hermes renders SPY quote flow as a real-time bubble chart of cumulative one-second NBBO bid and ask size, positioned at price, sized by quoted shares and colored by imbalance.
Read this on a live chart.
Hermes puts dealer positioning next to price through the session. Free to use.