> ## Documentation Index
> Fetch the complete documentation index at: https://docs.darvas.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Order blocks

> Detect order blocks (engulfing bars with volume confirmation) and draw them as Box entities that extend forward.

## What this builds

* Bullish order blocks: bearish bar followed by a bullish engulf with above-average volume
* Bearish order blocks: bullish bar followed by a bearish engulf with above-average volume
* Each block drawn as a `Box` with `extend: "right"` so it projects into future bars
* Box turns gray when price trades through the level (mitigation)

## Full script

```js theme={null}
// overlay = true
const volMult    = input.float("Volume multiplier", 1.5, { min: 1.0, max: 5.0, step: 0.1 });
const volLen     = input.int("Volume MA length", 20, { min: 5 });
const bullColor  = input.color("Bullish OB color", "#22c55e25");
const bearColor  = input.color("Bearish OB color", "#ef444425");
const bullBorder = input.color("Bullish border",   "#22c55eFF");
const bearBorder = input.color("Bearish border",   "#ef4444FF");
const mitColor   = input.color("Mitigated color",  "#6b728040");

onBar(() => {
  const vol    = ctx.volume();
  const volMa  = ta.sma(ctx.volume, volLen);
  const isHighVol = !na(volMa) && vol > volMa * volMult;

  const prevBear = ctx.open(1) > ctx.close(1);
  const prevBull = ctx.open(1) < ctx.close(1);
  const curBull  = ctx.close() > ctx.open();
  const curBear  = ctx.close() < ctx.open();

  const bullEngulf = prevBear && curBull && ctx.close() > ctx.open(1) && isHighVol;
  const bearEngulf = prevBull && curBear && ctx.close() < ctx.open(1) && isHighVol;

  const prevBar = ctx.i() - 1;

  if (bullEngulf) {
    Box(`bull_ob_${prevBar}`, {
      x1: prevBar,     y1: ctx.low(1),
      x2: ctx.i() + 1, y2: ctx.open(1),
      color: bullColor,
      borderColor: bullBorder,
      borderWidth: 1,
      extend: "right",
      text: "Bull OB",
      textColor: bullBorder,
      textSize: "xs",
      textHAlign: "left",
      textVAlign: "top",
    });
  }

  if (bearEngulf) {
    Box(`bear_ob_${prevBar}`, {
      x1: prevBar,     y1: ctx.open(1),
      x2: ctx.i() + 1, y2: ctx.high(1),
      color: bearColor,
      borderColor: bearBorder,
      borderWidth: 1,
      extend: "right",
      text: "Bear OB",
      textColor: bearBorder,
      textSize: "xs",
      textHAlign: "left",
      textVAlign: "top",
    });
  }

  // Mitigation: fade boxes that price has traded through
  // (Simplified: check if current close is inside any recent box)
  // For a production indicator, track active OB levels in Series
});
```

## Mitigation tracking (advanced)

To detect when price mitigates an OB (trades through it), store the box levels in `Series`:

```js theme={null}
const obHigh = Series("ob-high");
const obLow  = Series("ob-low");
const obBar  = Series("ob-bar");

onBar(() => {
  // ... (bullEngulf detection as above)

  if (bullEngulf) {
    obLow.set(ctx.low(1));
    obHigh.set(ctx.open(1));
    obBar.set(ctx.i() - 1);
  } else {
    obLow.set(obLow.get(1));
    obHigh.set(obHigh.get(1));
    obBar.set(obBar.get(1));
  }

  // Check mitigation: close trades below OB low
  const activeObBar = obBar.get();
  if (!na(activeObBar) && ctx.close() < obLow.get()) {
    Box(`bull_ob_${activeObBar}`, {
      x1: activeObBar, y1: obLow.get(),
      x2: ctx.i(),     y2: obHigh.get(),
      color: mitColor,
      borderColor: "#6b7280FF",
      borderWidth: 1,
    });
  }
});
```

## Notes

* `extend: "right"` makes the box grow forward in time until explicitly constrained by updating `x2`.
* Use unique keys (`bull_ob_${prevBar}`) so each detected block gets its own persistent slot.
* Box entities count toward the [500-per-type entity budget](/reference/api-limits).

## Related pages

<CardGroup cols={2}>
  <Card title="Box entity" href="/entities/box">
    Full Box options including extend.
  </Card>

  <Card title="Series" href="/essentials/series">
    Tracking active OB levels across bars.
  </Card>

  <Card title="API limits" href="/reference/api-limits">
    500 Box entity budget.
  </Card>
</CardGroup>