Enable offline data

Cloud Firestore supports offline data persistence. This feature caches a copy of the Cloud Firestore data that your app is actively using, so your app can access the data when the device is offline. You can write, read, listen to, and query the cached data. When the device comes back online, Cloud Firestore synchronizes any local changes made by your app to the data stored remotely in Cloud Firestore.

To use offline persistence, you don't need to make any changes to the code that you use to access Cloud Firestore data. With offline persistence enabled, the Cloud Firestore client library automatically manages online and offline data access and synchronizes local data when the device is back online.

Configure offline persistence

When you initialize Cloud Firestore, you can enable or disable offline persistence:

• For Android and iOS, offline persistence is enabled by default. To disable persistence, set the PersistenceEnabled option to false.
• For the web, offline persistence is disabled by default. To enable persistence, call the enablePersistence method. Cloud Firestore's cache isn't automatically cleared between sessions. Consequently, if your web app handles sensitive information, make sure to ask the user if they're on a trusted device before enabling persistence.

firebase.initializeApp({
  apiKey: '### FIREBASE API KEY ###',
  authDomain: '### FIREBASE AUTH DOMAIN ###',
  projectId: '### CLOUD FIRESTORE PROJECT ID ###',
}
);

firebase.firestore().enablePersistence()
  .catch(function(err) {
      if (err.code == 'failed-precondition') {
          // Multiple tabs open, persistence can only be enabled
          // in one tab at a a time.
          // ...
      } else if (err.code == 'unimplemented') {
          // The current browser does not support all of the
          // features required to enable persistence
          // ...
      }
  });
// Subsequent queries will use persistence, if it was enabled successfully
test.firestore.js
  

let settings = FirestoreSettings()
settings.isPersistenceEnabled = true

// Any additional options
// ...

// Enable offline data persistence
let db = Firestore.firestore()
db.settings = settings
ViewController.swift

FIRFirestoreSettings *settings = [[FIRFirestoreSettings alloc] init];
settings.persistenceEnabled = YES;

// Any additional options
// ...

// Enable offline data persistence
FIRFirestore *db = [FIRFirestore firestore];
db.settings = settings;
ViewController.m
  

FirebaseFirestoreSettings settings = new FirebaseFirestoreSettings.Builder()
        .setPersistenceEnabled(true)
        .build();
db.setFirestoreSettings(settings);
DocSnippets.java

val settings = FirebaseFirestoreSettings.Builder()
        .setPersistenceEnabled(true)
        .build()
db.firestoreSettings = settings
DocSnippets.kt

Listen to offline data

While the device is offline, if you have enabled offline persistence, your listeners will receive listen events when the locally cached data changes. You can listen to documents, collections, and queries.

To check whether you're receiving data from the server or the cache, use the fromCache property on the SnapshotMetadata in your snapshot event. If fromCache is true, the data came from the cache and might be stale or incomplete. If fromCache is false, the data is complete and current with the latest updates on the server.

By default, no event is raised if only the SnapshotMetadata changed. If you rely on the fromCache values, specify the includeMetadataChanges listen option when you attach your listen handler.

db.collection("cities").where("state", "==", "CA")
  .onSnapshot({ includeMetadataChanges: true }, function(snapshot) {
      snapshot.docChanges().forEach(function(change) {
          if (change.type === "added") {
              console.log("New city: ", change.doc.data());
          }

          var source = snapshot.metadata.fromCache ? "local cache" : "server";
          console.log("Data came from " + source);
      });
  });
test.firestore.js
 

// Listen to metadata updates to receive a server snapshot even if
// the data is the same as the cached data.
db.collection("cities").whereField("state", isEqualTo: "CA")
    .addSnapshotListener(includeMetadataChanges: true) { querySnapshot, error in
        guard let snapshot = querySnapshot else {
            print("Error retreiving snapshot: \(error!)")
            return
        }

        for diff in snapshot.documentChanges {
            if diff.type == .added {
                print("New city: \(diff.document.data())")
            }
        }

        let source = snapshot.metadata.isFromCache ? "local cache" : "server"
        print("Metadata: Data fetched from \(source)")
}
ViewController.swift

// Listen to metadata updates to receive a server snapshot even if
// the data is the same as the cached data.
[[[db collectionWithPath:@"cities"] queryWhereField:@"state" isEqualTo:@"CA"]
    addSnapshotListenerWithIncludeMetadataChanges:YES
    listener:^(FIRQuerySnapshot *snapshot, NSError *error) {
      if (snapshot == nil) {
        NSLog(@"Error retreiving snapshot: %@", error);
        return;
      }
      for (FIRDocumentChange *diff in snapshot.documentChanges) {
        if (diff.type == FIRDocumentChangeTypeAdded) {
          NSLog(@"New city: %@", diff.document.data);
        }
      }

      NSString *source = snapshot.metadata.isFromCache ? @"local cache" : @"server";
      NSLog(@"Metadata: Data fetched from %@", source);
    }];
ViewController.m
  

db.collection("cities").whereEqualTo("state", "CA")
        .addSnapshotListener(MetadataChanges.INCLUDE, new EventListener<QuerySnapshot>() {
            @Override
            public void onEvent(@Nullable QuerySnapshot querySnapshot,
                                @Nullable FirebaseFirestoreException e) {
                if (e != null) {
                    Log.w(TAG, "Listen error", e);
                    return;
                }

                for (DocumentChange change : querySnapshot.getDocumentChanges()) {
                    if (change.getType() == Type.ADDED) {
                        Log.d(TAG, "New city:" + change.getDocument().getData());
                    }

                    String source = querySnapshot.getMetadata().isFromCache() ?
                            "local cache" : "server";
                    Log.d(TAG, "Data fetched from " + source);
                }

            }
        });
DocSnippets.java

db.collection("cities").whereEqualTo("state", "CA")
        .addSnapshotListener(MetadataChanges.INCLUDE, EventListener<QuerySnapshot> { querySnapshot, e ->
            if (e != null) {
                Log.w(TAG, "Listen error", e)
                return@EventListener
            }

            for (change in querySnapshot!!.documentChanges) {
                if (change.type == DocumentChange.Type.ADDED) {
                    Log.d(TAG, "New city: ${change.document.data}")
                }

                val source = if (querySnapshot.metadata.isFromCache)
                    "local cache"
                else
                    "server"
                Log.d(TAG, "Data fetched from $source")
            }
        })
DocSnippets.kt

Get offline data

If you get a document while the device is offline, Cloud Firestore returns data from the cache. If the cache does not contain data for that document, or the document does not exist, the get call returns an error.

Query offline data

Querying works with offline persistence. You can retrieve the results of queries with either a direct get or by listening, as described in the preceding sections. You can also create new queries on locally persisted data while the device is offline, but the queries will initially run only against the cached documents.

Disable and enable network access

You can use the method below to disable network access for your Cloud Firestore client. While network access is disabled, all snapshot listeners and document requests retrieve results from the cache. Write operations are queued until network access is re-enabled.

firebase.firestore().disableNetwork()
    .then(function() {
        // Do offline actions
        // ...
    });
test.firestore.js
  

Firestore.firestore().disableNetwork { (error) in
    // Do offline things
    // ...
}
ViewController.swift

[[FIRFirestore firestore] disableNetworkWithCompletion:^(NSError *_Nullable error) {
  // Do offline actions
  // ...
}];
ViewController.m
  

db.disableNetwork()
        .addOnCompleteListener(new OnCompleteListener<Void>() {
            @Override
            public void onComplete(@NonNull Task<Void> task) {
                // Do offline things
                // ...
            }
        });
DocSnippets.java

db.disableNetwork().addOnCompleteListener {
    // Do offline things
    // ...
}
DocSnippets.kt

Use the following method to re-enable network access:

firebase.firestore().enableNetwork()
    .then(function() {
        // Do online actions
        // ...
    });
test.firestore.js
  

Firestore.firestore().enableNetwork { (error) in
    // Do online things
    // ...
}
ViewController.swift

[[FIRFirestore firestore] enableNetworkWithCompletion:^(NSError *_Nullable error) {
  // Do online actions
  // ...
}];
ViewController.m
  

db.enableNetwork()
        .addOnCompleteListener(new OnCompleteListener<Void>() {
            @Override
            public void onComplete(@NonNull Task<Void> task) {
                // Do online things
                // ...
            }
        });
DocSnippets.java

db.enableNetwork().addOnCompleteListener {
    // Do online things
    // ...
}
DocSnippets.kt