---
title: preferredThicknessFraction
framework: appkit
role: symbol
role_heading: Instance Property
path: appkit/nssplitviewitem/preferredthicknessfraction
---

# preferredThicknessFraction

The preferred thickness of the split view item relative to the split view.

## Declaration

```swift
var preferredThicknessFraction: CGFloat { get set }
```

## Discussion

Discussion This value represents the proportion of the split view that you want the split view item to occupy on a scale of 0.0 to 1.0. The system uses this value to adjust the thickness of the item in relation to other items when a user double-clicks a neighboring divider, and when the app enters full-screen mode. The default value of this property is unspecifiedDimension, which means the item doesn’t resize when a user double-clicks the divider, and the system preserves the absolute size when the app enters full-screen mode.

## See Also

### Managing the item thickness

- [automaticMaximumThickness](appkit/nssplitviewitem/automaticmaximumthickness.md)
- [minimumThickness](appkit/nssplitviewitem/minimumthickness.md)
- [maximumThickness](appkit/nssplitviewitem/maximumthickness.md)
- [unspecifiedDimension](appkit/nssplitviewitem/unspecifieddimension.md)