# Removal of AssetManifest.json

> Built Flutter apps will no longer include an AssetManifest.json asset file.




:::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 apps included an asset file named `AssetManifest.json`.
This file effectively contains a list of assets.
Application code can read it using the [`AssetBundle`][] API to
determine what assets are available at runtime.

The `AssetManifest.json` file is an undocumented implementation detail.
It's no longer used by the framework, and it's planned to
no longer generate it in a future release of Flutter.
If your app's code needs to get a list of available assets,
use the [`AssetManifest`][] API instead.

## Migration guide

### Reading asset manifest from Flutter application code

Before:

```dart
import 'dart:convert';
import 'package:flutter/services.dart';

void readAssetList() async {
  final assetManifestContent = await rootBundle.loadString('AssetManifest.json');
  final decodedAssetManifest =
      json.decode(assetManifestContent) as Map<String, Object?>;
  final assets = decodedAssetManifest.keys.toList().cast<String>();
}
```

After:

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

void readAssetList() async {
  final assetManifest = await AssetManifest.loadFromAssetBundle(rootBundle);
  final assets = assetManifest.listAssets();
}
```

### Reading asset manifest information from Dart code outside of a Flutter app

The `flutter` CLI tool generates a new file, `AssetManifest.bin`.
This replaces `AssetManifest.json`.
This file contains the same information as `AssetManifest.json`,
but in a different format.
If you need to read this file from code that isn't part of a Flutter app, and
therefore can't use the [`AssetManifest`][] API,
you can still parse the file yourself.

The [`standard_message_codec`][] package can be used to parse the contents.

```dart
import 'dart:io';
import 'dart:typed_data';

import 'package:standard_message_codec/standard_message_codec.dart';

void main() {
  // The path to AssetManifest.bin depends on the target platform.
  final pathToAssetManifest = './build/web/assets/AssetManifest.bin';
  final manifest = File(pathToAssetManifest).readAsBytesSync();
  final decoded = const StandardMessageCodec()
      .decodeMessage(ByteData.sublistView(manifest));
  final assets = decoded.keys.cast<String>().toList();
}
```

Keep in mind that `AssetManifest.bin` is an implementation detail of Flutter.
Reading this file isn't an officially supported workflow.
The contents or format of the file might change in
a future Flutter release without an announcement.

## Timeline

`AssetManifest.json` will no longer be generated starting with
the fourth stable release after 3.19 or one year after the release of 3.19,
whichever comes later.

## References

Relevant issues:

* When building a Flutter app, the flutter tool generates an
  `AssetManifest.json` file that's unused by the framework [(Issue #143577)][]

Relevant PR:

* [Remove deprecated `AssetManifest.json` file][PR 172594]

[`AssetBundle`]: https://api.flutter.dev/flutter/services/AssetBundle-class.html
[`AssetManifest`]: https://api.flutter.dev/flutter/services/AssetManifest-class.html
[(Issue #143577)]: https://github.com/flutter/flutter/issues/143577
[`standard_message_codec`]: https://pub.dev/packages/standard_message_codec
[PR 172594]: https://github.com/flutter/flutter/pull/172594