Bounding Boxes

Draw live rectangles around detected barcodes as the user moves the camera around.

What are bounding boxes?

When the scanner detects a barcode, it draws a rectangle around it on screen. This gives users a visual confirmation that the scanner is actively tracking a code — even before the final result fires.

It's a small detail that makes the scanning experience feel a lot more polished.

Live bounding box tracking a detected code

Enabling bounding boxes

Pass a boundingBox config to the Scanner:

<Scanner
  style={StyleSheet.absoluteFill}
  onCodeScanned={(result) => console.log(result.data)}
  boundingBox={{
    enabled: true,
  }}
/>

That's enough to get the default white box around detected codes.

Customizing the style

<Scanner
  style={StyleSheet.absoluteFill}
  onCodeScanned={(result) => console.log(result.data)}
  boundingBox={{
    enabled: true,
    borderColor: '#00E676',       // Green border
    borderWidth: 3,
    borderRadius: 10,             // Rounded corners
    fillColor: '#00E67620',       // Semi-transparent green fill
    showText: true,               // Show the decoded text
    textColor: '#000000',
    textSize: 13,
    textBackgroundColor: '#FFFFFF',
  }}
/>

Showing the decoded text

You can display the actual scanned value inside or near the bounding box:

boundingBox={{
  enabled: true,
  showText: true,
  textColor: '#000000',
  textSize: 14,
  textBackgroundColor: '#FFFFFFCC', // White with slight transparency
}}

This is useful for debug views or apps where the user should see exactly what was scanned before confirming.

Bounding boxes work naturally with scan regions. The box only appears when the code is inside the region — so if a code is partially visible outside the frame, no box appears. Once the user aligns the code inside the frame, the box shows up.

<Scanner
  style={StyleSheet.absoluteFill}
  onCodeScanned={(result) => console.log(result.data)}
  scanRegion={{
    enabled: true,
    width: 280,
    height: 280,
  }}
  boundingBox={{
    enabled: true,
    borderColor: '#FFFFFF',
    borderWidth: 2,
    showText: false,
  }}
/>

All options

Option	Type	Default	Description
`enabled`	`boolean`	`true`	Show bounding boxes
`borderColor`	`string`	`#FFFFFF`	Box border color
`borderWidth`	`number`	`4`	Border thickness in points/dp
`borderRadius`	`number`	`12`	Rounded corner radius
`fillColor`	`string`	—	Optional fill color. Use `#RRGGBBAA` for transparency
`showText`	`boolean`	`true`	Show the decoded value as a label
`textColor`	`string`	`#000000`	Label text color
`textSize`	`number`	`14`	Label font size
`textBackgroundColor`	`string`	`#FFFFFF`	Label background color

Color format

All color values use hex strings. You can use:

#RRGGBB — fully opaque color, e.g. #FF0000 for red
#RRGGBBAA — color with alpha, e.g. #FF000080 for 50% transparent red

The alpha channel is the last two characters, not the first. This is important — if you get the order wrong, the color will look different than expected.

A note on performance

Bounding boxes are drawn as native overlays on top of the camera preview. They don't go through the JavaScript bridge per frame, so they won't slow down your app even during fast movement.