Font loading fails due to removal of `AssetManifest.json` support in Flutter

[toda-bps]

Package

google_fonts

Existing issue?

• I checked the existing issues

Related issue

• https://github.com/material-foundation/google_fonts_flutter/issues/26

What happened?

It appears that Flutter no longer supports AssetManifest.json as of the following commit:

• Remove deprecated AssetManifest.json file (#172594)
  • flutter/flutter@0e7da1d

As a result, the attempt to load AssetManifest.json in the google_fonts package is failing, which prevents fonts from being loaded.

The failing code is located here:

flutter-packages/packages/google_fonts/lib/src/asset_manifest.dart

Lines 34 to 37 in 3d0b27b

	final jsonString = await rootBundle.loadString(
	'AssetManifest.json',
	cache: enableCache,
	);

final jsonString = await rootBundle.loadString(
  'AssetManifest.json',
  cache: enableCache,
);

This results in the following log output:

[  +39 ms] flutter: [ 2025-07-28 23:37:03.110893 ] Unable to load asset: "AssetManifest.json".
[        ] flutter: The asset does not exist or has empty data.
[        ] flutter: Error: google_fonts was unable to load font RobotoMono-Regular because the following exception occurred:
[        ] Unable to load asset: "AssetManifest.json".
[        ] The asset does not exist or has empty data.
[        ] flutter:
[        ] See https://docs.flutter.dev/development/data-and-backend/networking#platform-notes.
[        ] flutter: If troubleshooting doesn't solve the problem, please file an issue at

Relevant log output

[!] Flutter (Channel [user-branch], 3.33.0-1.0.pre-1135, on macOS 15.5 24F74 darwin-arm64, locale ja-JP) [241ms]
    ! Flutter version 3.33.0-1.0.pre-1135 on channel [user-branch] at /Users/bps/buildroot/flutter_master
      Currently on an unknown channel. Run `flutter channel` to switch to an official channel.
      If that doesn't fix the issue, reinstall Flutter by following instructions at https://flutter.dev/setup.
    ! Upstream repository unknown source is not a standard remote.
      Set environment variable "FLUTTER_GIT_URL" to unknown source to dismiss this error.
    • Framework revision 0e7da1d019 (3 days ago), 2025-07-25 13:20:34 -0700
    • Engine revision 0abc2ec292
    • Dart version 3.10.0 (build 3.10.0-28.0.dev)
    • DevTools version 2.48.0
    • Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android, enable-ios, cli-animations, enable-native-assets
    • If those were intentional, you can disregard the above warnings; however it is recommended to use "git" directly to perform update checks and upgrades.

[✓] Android toolchain - develop for Android devices (Android SDK version 35.0.0) [1,012ms]
    • Android SDK at /Users/bps/Library/Android/sdk
    • Emulator version 35.6.11.0 (build_id 13610412) (CL:N/A)
    • Platform android-36, build-tools 35.0.0
    • ANDROID_HOME = /Users/bps/Library/Android/sdk
    • Java binary at: /Users/bps/Library/Java/JavaVirtualMachines/jbr-17.0.12/Contents/Home/bin/java
      This JDK is specified in your Flutter configuration.
      To change the current JDK, run: `flutter config --jdk-dir="path/to/jdk"`.
    • Java version OpenJDK Runtime Environment JBR-17.0.12+1-1087.25-nomod (build 17.0.12+1-b1087.25)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 16.2) [515ms]
    • Xcode at /Applications/Xcode16.2.app/Contents/Developer
    • Build 16C5032a
    • CocoaPods version 1.16.2

[✓] Chrome - develop for the web [4ms]
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Connected device (2 available) [5.7s]
    • macOS (desktop) • macos  • darwin-arm64   • macOS 15.5 24F74 darwin-arm64
    • Chrome (web)    • chrome • web-javascript • Google Chrome 138.0.7204.169

[✓] Network resources [1,010ms]
    • All expected network resources are available.

! Doctor found issues in 1 category.

[guidezpl]

Should be fixed by next version, closing

[anowotny]

This is still an issue when using Flutter 3.38.2

The asset does not exist or has empty data.
flutter: If troubleshooting doesn't solve the problem, please file an issue at https://github.com/material-foundation/flutter-packages/issues/new/choose.
flutter: Error: google_fonts was unable to load font Raleway-Bold because the following exception occurred:
Unable to load asset: "AssetManifest.json".
The asset does not exist or has empty data.
flutter: If troubleshooting doesn't solve the problem, please file an issue at https://github.com/material-foundation/flutter-packages/issues/new/choose.
flutter: Error: google_fonts was unable to load font Raleway-SemiBold because the following exception occurred:
Unable to load asset: "AssetManifest.json".
The asset does not exist or has empty data.
flutter: If troubleshooting doesn't solve the problem, please file an issue at https://github.com/material-foundation/flutter-packages/issues/new/choose.
flutter: Error: google_fonts was unable to load font Raleway-Medium because the following exception occurred:
Unable to load asset: "AssetManifest.json".
The asset does not exist or has empty data.
flutter: If troubleshooting doesn't solve the problem, please file an issue at https://github.com/material-foundation/flutter-packages/issues/new/choose.
[ERROR:flutter/runtime/dart_vm_initializer.cc(40)] Unhandled Exception: Unable to load asset: "AssetManifest.json".
The asset does not exist or has empty data.
#0      PlatformAssetBundle.load.<anonymous closure> (package:flutter/src/services/asset_bundle.dart:332:13)
<asynchronous suspension>
#1      AssetBundle.loadString (package:flutter/src/services/asset_bundle.dart:92:27)
<asynchronous suspension>
#2      AssetManifest._loadAssetManifestJson (package:google_fonts/src/asset_manifest.dart:34:26)
<asynchronous suspension>
#3      loadFontIfNecessary (package:google_fonts/src/google_fonts_base.dart:150:31)
<asynchronous suspension>
#4      googleFontsTextStyle.<anonymous closure> (package:google_fonts/src/google_fonts_base.dart:115:22)
<asynchronous suspension>
[ERROR:flutter/runtime/dart_vm_initializer.cc(40)] Unhandled Exception: Unable to load asset: "AssetManifest.json".
The asset does not exist or has empty data.
#0      PlatformAssetBundle.load.<anonymous closure> (package:flutter/src/services/asset_bundle.dart:332:13)
<asynchronous suspension>
#1      AssetBundle.loadString (package:flutter/src/services/asset_bundle.dart:92:27)
<asynchronous suspension>
#2      AssetManifest._loadAssetManifestJson (package:google_fonts/src/asset_manifest.dart:34:26)
<asynchronous suspension>
#3      loadFontIfNecessary (package:google_fonts/src/google_fonts_base.dart:150:31)
<asynchronous suspension>
#4      googleFontsTextStyle.<anonymous closure> (package:google_fonts/src/google_fonts_base.dart:115:22)
<asynchronous suspension>
[ERROR:flutter/runtime/dart_vm_initializer.cc(40)] Unhandled Exception: Unable to load asset: "AssetManifest.json".
The asset does not exist or has empty data.
#0      PlatformAssetBundle.load.<anonymous closure> (package:flutter/src/services/asset_bundle.dart:332:13)
<asynchronous suspension>
#1      AssetBundle.loadString (package:flutter/src/services/asset_bundle.dart:92:27)
<asynchronous suspension>
#2      AssetManifest._loadAssetManifestJson (package:google_fonts/src/asset_manifest.dart:34:26)
<asynchronous suspension>
#3      loadFontIfNecessary (package:google_fonts/src/google_fonts_base.dart:150:31)
<asynchronous suspension>
#4      googleFontsTextStyle.<anonymous closure> (package:google_fonts/src/google_fonts_base.dart:115:22)
<asynchronous suspension>
[ERROR:flutter/runtime/dart_vm_initializer.cc(40)] Unhandled Exception: Unable to load asset: "AssetManifest.json".
The asset does not exist or has empty data.
#0      PlatformAssetBundle.load.<anonymous closure> (package:flutter/src/services/asset_bundle.dart:332:13)
<asynchronous suspension>
#1      AssetBundle.loadString (package:flutter/src/services/asset_bundle.dart:92:27)
<asynchronous suspension>
#2      AssetManifest._loadAssetManifestJson (package:google_fonts/src/asset_manifest.dart:34:26)
<asynchronous suspension>
#3      loadFontIfNecessary (package:google_fonts/src/google_fonts_base.dart:150:31)
<asynchronous suspension>
#4      googleFontsTextStyle.<anonymous closure> (package:google_fonts/src/google_fonts_base.dart:115:22)
<asynchronous suspension>```

EDIT: Resolved, my google_fonts version was pre-6.3.2

[gasparpd]

Yep, solved after update google_fonts to ^6.3.0