# Page transition builders reorganization

> CupertinoPageTransitionsBuilder has been moved from the Material library to the Cupertino library where it belongs.




:::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

`CupertinoPageTransitionsBuilder` has been relocated from
`package:flutter/material.dart` to `package:flutter/cupertino.dart`.

## Background

Flutter provides several page transition builders that
control how routes animate when navigating between pages.
These builders are used with `PageTransitionsTheme` to
customize transitions per platform.

The available page transition builders are:

| Builder | Library | Description |
|---------|---------|-------------|
| `FadeUpwardsPageTransitionsBuilder` | Material | Default transition before Material 3 |
| `OpenUpwardsPageTransitionsBuilder` | Material | Vertical slide transition |
| `ZoomPageTransitionsBuilder` | Material | Zoom transition (Material 3 default) |
| `PredictiveBackPageTransitionsBuilder` | Material | Android predictive back gesture support |
| `CupertinoPageTransitionsBuilder` | **Cupertino** | iOS-style horizontal slide transition |

{:.table}

Previously, `CupertinoPageTransitionsBuilder` was defined in
the Material library alongside the other builders.
This class is semantically a Cupertino component because
its implementation uses Cupertino transition mixins and
provides iOS-style navigation animations.

This move improves code organization and allows Cupertino apps to
use this builder without depending on the Material library.

## Migration guide

If you use `CupertinoPageTransitionsBuilder` and
only import `package:flutter/material.dart`,
add an import for `package:flutter/cupertino.dart`.

Code before migration:

```dart
import 'package:flutter/material.dart';

final pageTransitionsTheme = PageTransitionsTheme(
  builders: {
    TargetPlatform.android: ZoomPageTransitionsBuilder(),
    TargetPlatform.iOS: CupertinoPageTransitionsBuilder(),
  },
);
```

Code after migration:

```dart
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

final pageTransitionsTheme = PageTransitionsTheme(
  builders: {
    TargetPlatform.android: ZoomPageTransitionsBuilder(),
    TargetPlatform.iOS: CupertinoPageTransitionsBuilder(),
  },
);
```

If your app already imports both packages, no changes are needed.

## Timeline

Landed in version: 3.43.0-0.1.pre<br>
In stable release: 3.44

## References

Relevant PRs:

* [Decouple CupertinoPageTransitionsBuilder from Material][pr-179776]

[pr-179776]: https://github.com/flutter/flutter/pull/179776