On-balance volume
Running volume total that adds a bar's volume on up-closes and subtracts it on down-closes; read its trend against price.
OBV compares each one-minute close with the close before it. If the close is higher, that bar's whole volume is added to a running total; if lower, the whole volume is subtracted; if unchanged, the total stays put. The total starts at zero on the first bar on the chart, so it measures net volume flow over the window rather than a price level.
How to read it
- The line sits in its own pane below the price, in volume units.
- A rising line means most of the recent volume came on up-closes; a falling line means it came on down-closes.
- The classic read is divergence: price makes a new high while the line does not, or price falls while the line holds up.
- Read the slope and the turns, not the number, because the level depends on where the chart's window starts.
What it outputs
- OBV
- Running total of volume signed by close direction. Adds the bar's volume on an up-close, subtracts it on a down-close, keeps it on an unchanged close.
Pitfalls
- The level is a sum from the first bar on the chart, so the same bar reads differently on another window. On Sept 2026 SPY the total sat mostly below zero (median -8.4M), so a negative reading was normal there.
- Any close change moves the total by that bar's full volume, so a one-cent tick counts the same as a large move. It records volume direction, not how far price moved.
- On the Sept 2026 SPY one-minute sample it barely tracked price (correlation -0.08 with close), so divergences here are close to noise and no threshold is established.