# Deprecated `cacheExtent` and `cacheExtentStyle`

> The `cacheExtent` and `cacheExtentStyle` properties are deprecated. They are replaced by `scrollCacheExtent` with a `ScrollCacheExtent` object.




:::important
These breaking change docs are accurate, as of the release
under which they are published. Over time, the
workarounds described here might become inaccurate.
We don't, in general, keep these breaking change docs up
to date as of each release.

The [breaking change index file](/release/breaking-changes)
lists the docs created for each release.
:::


## Summary

Flutter 3.44 deprecates `cacheExtent` and `cacheExtentStyle`
in scrolling-related widgets, such as
`ListView`, `GridView`, `CustomScrollView`, and `Viewport`,
and their corresponding render objects, such as `RenderViewport`.
The new `scrollCacheExtent` property encapsulates
both the value and the caching strategy (pixels or viewport).

## Background

Previously, `cacheExtent` was a `double` and
`cacheExtentStyle` determined how that `double` was interpreted
(either as pixels or as a fraction of the viewport).
This split made the setting harder to understand.

The new `scrollCacheExtent` property uses a `ScrollCacheExtent` object that
explicitly encapsulates both the value and
the caching strategy (pixels or viewport),
which provides type safety and clearer intent.

## Migration guide

### Widget layer

#### `cacheExtent` (pixels)

If your code uses `cacheExtent`,
which defaults to pixels,
use `scrollCacheExtent` with `ScrollCacheExtent.pixels`.

**Before:**

```dart
ListView(
  cacheExtent: 500.0,
  children: // ...
)
```

**After:**

```dart
ListView(
  scrollCacheExtent: const ScrollCacheExtent.pixels(500.0),
  children: // ...
)
```

#### `cacheExtentStyle` (viewport)

If your code uses `cacheExtent` with `CacheExtentStyle.viewport`,
which is common in `Viewport`,
use `scrollCacheExtent` with `ScrollCacheExtent.viewport`.

**Before:**

```dart
Viewport(
  cacheExtent: 0.5,
  cacheExtentStyle: CacheExtentStyle.viewport,
  slivers: // ...
)
```

**After:**

```dart
Viewport(
  scrollCacheExtent: const ScrollCacheExtent.viewport(0.5),
  slivers: // ...
)
```

### Render object layer

If your code manually sets properties on
`RenderViewport` or a similar render object,
use `scrollCacheExtent`.

**Before:**

```dart
renderViewport.cacheExtent = 500.0;
renderViewport.cacheExtentStyle = CacheExtentStyle.pixel;
```

**After:**

```dart
renderViewport.scrollCacheExtent = const ScrollCacheExtent.pixels(500.0);
```

## Timeline

Landed in version: 3.41.0-0.0.pre<br>
In stable release: 3.44

## References

API documentation:

* [`ScrollCacheExtent`][]
* [`ScrollView.scrollCacheExtent`][]
* [`RenderViewportBase.scrollCacheExtent`][]

Relevant PRs:

* [Introduce ScrollCacheExtent][pr-181092]

[`ScrollCacheExtent`]: https://api.flutter.dev/flutter/rendering/ScrollCacheExtent-class.html
[`ScrollView.scrollCacheExtent`]: https://api.flutter.dev/flutter/widgets/ScrollView/scrollCacheExtent.html
[`RenderViewportBase.scrollCacheExtent`]: https://api.flutter.dev/flutter/rendering/RenderViewportBase/scrollCacheExtent.html

[pr-181092]: https://github.com/flutter/flutter/pull/181092