Firebase Cloud Storage Skill

This skill defines how to correctly use Firebase Cloud Storage in Flutter applications.

When to Use

Use this skill when:

Setting up Cloud Storage in a Flutter project.
Uploading or downloading files.
Managing file metadata.
Handling Storage errors and monitoring upload progress.

1. Setup and Configuration

flutter pub add firebase_storage

import 'package:firebase_storage/firebase_storage.dart';

final storage = FirebaseStorage.instance;
// Or specify a bucket explicitly:
// final storage = FirebaseStorage.instanceFor(bucket: "gs://BUCKET_NAME");

Firebase Storage requires the Blaze (pay-as-you-go) plan.
Run flutterfire configure to update your Firebase config with the default Storage bucket name.

Security note: By default, a Cloud Storage bucket requires Firebase Authentication for any action. Configuring public access may also make App Engine files publicly accessible — restrict access again when you set up Authentication.

2. File Operations

Create a reference:

final storageRef = FirebaseStorage.instance.ref();
final fileRef = storageRef.child("uploads/file.jpg");

Upload:

final uploadTask = fileRef.putFile(file);
final snapshot = await uploadTask;
final downloadUrl = await snapshot.ref.getDownloadURL();

Download (in-memory):

final data = await fileRef.getData();

Download URL:

final downloadUrl = await fileRef.getDownloadURL();

Delete:

await fileRef.delete();

3. Metadata Management

Get metadata:

final metadata = await fileRef.getMetadata();
print('Content type: ${metadata.contentType}');
print('Size: ${metadata.size}');

Update metadata:

final newMetadata = SettableMetadata(
  contentType: "image/jpeg",
  customMetadata: {'uploaded_by': 'user123'},
);
await fileRef.updateMetadata(newMetadata);

Use custom metadata to store additional key/value pairs with your files.

4. Error Handling

Use try-catch with FirebaseException. Key error codes:

Code	Meaning
`storage/object-not-found`	File doesn't exist at the reference
`storage/bucket-not-found`	No bucket configured for Cloud Storage
`storage/project-not-found`	No project configured for Cloud Storage
`storage/quota-exceeded`	Storage quota exceeded
`storage/unauthenticated`	User needs to authenticate
`storage/unauthorized`	User lacks permission
`storage/retry-limit-exceeded`	Operation timeout exceeded

For quota-exceeded on the Spark plan, upgrade to Blaze.
Implement retry logic for network-related errors and timeouts.

5. Performance and Best Practices

Monitor upload progress:

final uploadTask = fileRef.putFile(file);
uploadTask.snapshotEvents.listen((TaskSnapshot snapshot) {
  print('Progress: ${(snapshot.bytesTransferred / snapshot.totalBytes) * 100}%');
});

Cancel uploads with uploadTask.cancel().
Pause / resume with uploadTask.pause() and uploadTask.resume().
Optimize file sizes before upload to reduce costs and improve performance.
Use Cloud Storage with Firestore for comprehensive data management.
Use the Firebase Local Emulator Suite for local development and testing.

6. Security

Use Firebase Security Rules to control access to files.
Combine Storage rules with Firebase Authentication for user-based access control.
Test security rules thoroughly before deploying to production.

firebase-storage