Crowdin Flutter SDK

The Crowdin Flutter SDK delivers all new translations from Crowdin project to the application immediately. So there is no need to update the application via Store to get the new version with the localization.

Example project  |  Crowdin Docs  |  Crowdin Enterprise Docs

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  • Load remote strings from Crowdin Over-The-Air Content Delivery Network
    • Built-in translations caching mechanism (enabled by default, can be disabled)
    • Network usage configuration (All, only Wi-Fi or Cellular)
    • Load static strings from the bundled ARB files (usable as a fallback for the CDN strings)
  • Real-Time Preview – all the translations that are done in the Editor can be shown in your version of the application in real-time. View the translations already made and the ones you're currently typing in.


  • Dart >=2.17.0


To configure Flutter SDK integration you need to:

  • Upload your .arb localization files to Crowdin. If you have ready translations, you can also upload them. Alternatively, you can use the Flutter .ARB String Exporter to export Flutter .arb from your Crowdin project strings.
  • Set up Distribution in Crowdin.
  • Set up SDK and enable Over-The-Air Content Delivery feature in your project.

Distribution is a CDN vault that mirrors the translated content of your project and is required for integration with the Flutter app.

To manage distributions, open the Crowdin project and go to the Translations > Over-The-Air Content Delivery section. You can create as many distributions as you need and select different files for each. You'll need to click the Release button next to the distribution each time you want to send new translations to the app.

To integrate SDK with your application you need to follow the step-by-step instructions:

  • First of all, your Flutter project should be internationalized using the flutter_localizations package. For more detail, see Setting up an internationalized app.

  • Create a project in Crowdin.

  • Upload your app_en.arb file to the created Crowdin project. Optionally, you can also Upload Existing Translations.

  • Set up a Distribution.

  • Add the crowdin_sdk dependency to your project:

      crowdin_sdk: ^0.6.3
        sdk: flutter
      intl: any
      generate: true
  • Run the following command to generate Crowdin localization:

    flutter pub run crowdin_sdk:gen

    As a result, the Crowdin_localizations.dart will be created in the {FLUTTER_PROJECT}/.dart_tool/flutter_gen/gen_l10n directory.

  • Update localizationsDelegates in your project:

    import 'package:flutter_gen/gen_l10n/app_localizations.dart';
    import 'package:crowdin_sdk/crowdin_sdk.dart';
    import 'package:flutter_gen/gen_l10n/crowdin_localizations.dart';
    Widget build(BuildContext context) {
      return MaterialApp(
        // ...
        localizationsDelegates: CrowdinLocalization.localizationsDelegates,
        supportedLocales: AppLocalizations.supportedLocales,
        // ...
  • Initialize Crowdin SDK in the main function of your application:

    void main() async {
      await Crowdin.init(
        distributionHash: 'distribution_hash', // Fill in with your distribution hash
        connectionType: InternetConnectionType.any,
        updatesInterval: const Duration(minutes: 15),
      // ...
  • Use the Crowdin.loadTranslations function to load translations from Crowdin for the specified locale:

    await Crowdin.loadTranslations(Locale('en'));

After receiving the translations, change the app locale as usual and the translations from Crowdin will be applied.


Config option Description
distributionHash Crowdin Distribution Hash
connectionType Network type to be used for translations download. Supported values are any, wifi, mobileData, ethernet
updatesInterval Translations update interval. Translations will not be updated more frequently than the designated time interval (default minimum is 15 minutes). Instead, it will use previously cached translations

Real-Time Preview

All translations done in the Crowdin Editor can be displayed in your version of the application in real-time. See the translations that have already been done and the ones you're typing.

Note: Real-Time Preview feature should not be used in production builds. Currently, this feature is available only for Android and iOS applications.


Add the following code to the Crowdin initialization:

void main() async {

  await Crowdin.init(
    distributionHash: 'distribution_hash',
    connectionType: InternetConnectionType.any,
    updatesInterval: const Duration(minutes: 15),
    withRealTimeUpdates: true, // use this parameter for enable/disable real-time preview functionality
    authConfigurations: CrowdinAuthConfig(
     clientId: 'clientId', // your clientId from Crowdin OAuth app
     clientSecret: 'clientSecret', // your client secret from Crowdin OAuth app
     redirectUri: 'redirectUri', // your redirect uri from Crowdin OAuth app
     organizationName: 'organizationName' // optional (only for Crowdin Enterprise)

  // ...

Wrap your app root widget with the CrowdinRealTimePreviewWidget:

Widget build(BuildContext context) {
  return CrowdinRealTimePreviewWidget(
    child: MaterialApp(
      // ...

      localizationsDelegates: CrowdinLocalization.localizationsDelegates,
      supportedLocales: AppLocalizations.supportedLocales,

      // ...

For OAuth App the redirect URL should match your app scheme. For example, for scheme <data android:scheme="crowdintest" />, redirect URL in Crowdin should be crowdintest://. Specify project.translation scope for the OAuth app on Crowdin.

For Android app, declare the following intent filter in android/app/src/main/AndroidManifest.xml:

<manifest ...>
<!-- ... other tags -->
<application ...>
  <activity ...>
    <!-- ... other tags -->

    <intent-filter android:autoVerify="true">
      <action android:name="android.intent.action.VIEW" />
      <category android:name="android.intent.category.DEFAULT" />
      <category android:name="android.intent.category.BROWSABLE" />
      <!-- Accepts URIs that begin with https://YOUR_HOST -->
      <data android:scheme="[YOUR_SCHEME]"/>

For iOS app, declare the scheme in ios/Runner/Info.plist:

<?xml ...>
<!-- ... other tags -->
    <!-- ... other tags -->


    <!-- ... other tags -->

Config options

Config option Description
withRealTimeUpdates Enable Real-Time Preview feature
authConfigurations CrowdinAuthConfig class that contains parameters for OAuth authorization
clientId Crowdin OAuth Client ID
clientSecret Crowdin OAuth Client Secret
redirectUri Crowdin OAuth redirect URL
organizationName An Organization domain name (for Crowdin Enterprise users only)

For more information about OAuth authorization in Crowdin, please check this article.

Note: To easily run your app in the Crowdin Editor, you can use Crowdin Appetize integration. It allows your translators to run this app in the Editor, see more context, and provide better translations.


  • The CDN feature does not update the localization files. if you want to add new translations to the localization files you need to do it yourself.

  • Once SDK receives the translations, it's stored on the device as application files for further sessions to minimize requests the next time the app starts. Storage time can be configured.

  • CDN caches all the translations in release and even when new translations are released in Crowdin, CDN may return them with a delay.

  • Since some languages have different language codes maintained by the intl package and by Crowdin (for example, intl uses "es" for the Spanish language, and Crowdin uses "es-ES"). For the following intl language codes Crowdin SDK uses equivalent language codes:

    • Armenian - hy: hy-AM
    • Chinese Simplified - zh: zh-CN
    • Gujarati - gu: gu-IN
    • Nepali - ne: ne-NP
    • Portuguese - pt: pt-PT
    • Punjabi - pa: pa-IN
    • Sinhala - si: si-LK
    • Spanish - es: es-ES
    • Swedish - sv: sv-SE
    • Urdu (India) - ur: ur-IN


If you would like to contribute, please read the Contributing Guidelines.

Seeking Assistance

If you find any problems or would like to suggest a feature, please feel free to submit an issue on GitHub at the Issues Page.


Crowdin Flutter SDK CDN feature is built with security in mind, which means minimal access possible from the end-user is required. When you decide to use Crowdin Flutter SDK, please make sure you’ve made the following information accessible to your end-users.

  • We use the advantages of Amazon Web Services (AWS) for our computing infrastructure. AWS has ISO 27001 certification and has completed multiple SSAE 16 audits. All the translations are stored at AWS servers.
  • When you use Crowdin Flutter SDK CDN – translations are uploaded to Amazon CloudFront to be delivered to the app and speed up the download. Keep in mind that your users download translations without any additional authentication.
  • We use encryption to keep your data private while in transit.
  • We do not store any Personally Identifiable Information (PII) about the end-user, but you can decide to develop the opt-out option inside your application to make sure your users have full control.


The Crowdin Flutter SDK is licensed under the MIT License.
See the LICENSE file distributed with this work for additional 
information regarding copyright ownership.

Except as contained in the LICENSE file, the name(s) of the above copyright 
holders shall not be used in advertising or otherwise to promote the sale, 
use or other dealings in this Software without prior written authorization.