Start with the best prices and spread
The best bid is the highest displayed buy limit; the best ask is the lowest displayed sell limit. Their difference is the spread. The midpoint is a reference halfway between them, not necessarily an executable price.
Always identify the market pair. BTCUSDT quantity and notional cannot be compared directly with another quote currency or venue without conversion and timing controls.
Read levels, cumulative depth, and notional
Each price level aggregates visible quantity. Cumulative depth adds levels from the best price outward. Notional depth multiplies base quantity by price, making the economic size easier to compare across nearby levels.
A fixed relative band such as 20 basis points scales with price and keeps bid and ask measurement distances symmetric. A wider band includes more liquidity but may be less relevant to immediate trading.
Shape can matter more than one total
Two books can have equal total depth but different shapes. Liquidity concentrated at the best level may interact immediately; the same amount placed near the edge of the band provides more distant resistance. Sudden gaps can increase potential slippage.
A depth chart is a snapshot of displayed intent. Watch how levels replenish, move, or disappear rather than treating a single wall as permanent.
How Market Tug uses depth
Market Tug synchronizes a Level 2 book and sums nearby bid and ask notional within 20 basis points of the midpoint. The resulting imbalance contributes 30% of mp-v1.1.0 pressure; executed flow contributes 70%.
If update sequencing breaks or the stream becomes stale, the depth component is not silently reused. The live product pauses until a trustworthy state is restored.