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Get started with Cloud Storage on Flutter

docs/storage/start.md

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Get started with Cloud Storage on Flutter

Cloud Storage for Firebase lets you upload and share user generated content, such as images and video, which allows you to build rich media content into your apps. Your data is stored in a Google Cloud Storage bucket — an exabyte scale object storage solution with high availability and global redundancy. Cloud Storage for Firebase lets you securely upload these files directly from mobile devices and web browsers, handling spotty networks with ease.

Before you begin {: #before-you-begin}

  1. If you haven't already, make sure you've completed the getting started guide for Flutter apps. This includes:

    • Creating a Firebase project.

    • Installing and initializing the Firebase SDKs for Flutter.

  2. Make sure your Firebase project is on the {{blaze_plan_with_link}}. If you're new to Firebase and Google Cloud, check if you're eligible for a $300 credit.

<<../_includes/_changes-sept-2024-notice.md>>

Create a default Cloud Storage bucket {:#create-default-bucket}

<<../_includes/_create-default-bucket.md>>

Set up public access {: #set_up_public_access}

Cloud Storage for Firebase provides a declarative rules language that lets you define how your data should be structured, how it should be indexed, and when your data can be read from and written to. By default, read and write access to Cloud Storage is restricted so only authenticated users can read or write data. To get started without setting up Firebase Authentication, you can configure your rules for public access.

This does make Cloud Storage open to anyone, even people not using your app, so be sure to restrict your Cloud Storage again when you set up authentication.

Add the Cloud Storage SDK to your app {:#add-sdk}

  1. From the root of your Flutter project, run the following command to install the plugin:

    bash
    flutter pub add firebase_storage

  2. Once complete, rebuild your Flutter application:

    bash
    flutter run

  3. Import the plugin in your Dart code:

    dart
    import 'package:firebase_storage/firebase_storage.dart';

Set up Cloud Storage {:#set-up-cloud-storage}

  1. Run flutterfire configure from your Flutter project directory. This updates the Firebase config file (firebase_options.dart) in your app's codebase so that it has the name of your default {{storage}} bucket.

    Note: Alternatively to updating your config file, you can explicitly specify the bucket name when you create an instance of FirebaseStorage (see next step). You can find the bucket name in the {{firebase_storage}} Files tab{: .external} of the {{name_appmanager}}.

  2. Access your Cloud Storage bucket by creating an instance of FirebaseStorage:

    dart
    final storage = FirebaseStorage.instance;

// Alternatively, explicitly specify the bucket name URL.
// final storage = FirebaseStorage.instanceFor(bucket: "gs://<var>BUCKET_NAME</var>");

You're ready to start using Cloud Storage!

Next step? Learn how to create a Cloud Storage reference.

Advanced setup

There are a few use cases that require additional setup:

The first use case is perfect if you have users across the world, and want to store their data near them. For instance, you can create buckets in the US, Europe, and Asia to store data for users in those regions to reduce latency.

The second use case is helpful if you have data with different access patterns. For instance: you can set up a multi-regional or regional bucket that stores pictures or other frequently accessed content, and a nearline or coldline bucket that stores user backups or other infrequently accessed content.

In either of these use cases, you'll want to use multiple Cloud Storage buckets.

The third use case is useful if you're building an app, like Google Drive, which lets users have multiple logged in accounts (for instance, a personal account and a work account). You can use a custom Firebase App instance to authenticate each additional account.

Use multiple Cloud Storage buckets {:#use_multiple_storage_buckets}

If you want to use a Cloud Storage bucket other than the default provided above, or use multiple Cloud Storage buckets in a single app, you can create an instance of FirebaseStorage that references your custom bucket:

dart
// Get a non-default Storage bucket
final storage = FirebaseStorage.instanceFor(bucket: "gs://my-custom-bucket");

Working with imported buckets

When importing an existing Cloud Storage bucket into Firebase, you'll have to grant Firebase the ability to access these files using the gsutil tool, included in the Google Cloud SDK:

bash
gcloud storage objects add-iam-policy-binding gs://YOUR-CLOUD-STORAGE-BUCKET \
    --member="serviceAccount:service-PROJECT_NUMBER@gcp-sa-firebasestorage.iam.gserviceaccount.com" \
    --role="roles/storage.objectViewer"

You can find your project number as described in the introduction to Firebase projects.

This does not affect newly created buckets, as those have the default access control set to allow Firebase. This is a temporary measure, and will be performed automatically in the future.

Use a custom Firebase App {:#use_a_custom_firebaseapp}

If you're building a more complicated app using a custom FirebaseApp, you can create an instance of FirebaseStorage initialized with that app:

dart
// Use a non-default App
final storage = FirebaseStorage.instanceFor(app: customApp);

Next steps