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
Cloud Firestore backend.
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.
When you initialize Cloud Firestore, you can enable or disable
offline persistence:
- For Android and Apple platforms, 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.
Web modular API
// Memory cache is the default if no config is specified.
initializeFirestore(app);
// This is the default behavior if no persistence is specified.
initializeFirestore(app, {localCache: memoryLocalCache()});
// Defaults to single-tab persistence if no tab manager is specified.
initializeFirestore(app, {localCache: persistentLocalCache(/*settings*/{})});
// Same as `initializeFirestore(app, {localCache: persistentLocalCache(/*settings*/{})})`,
// but more explicit about tab management.
initializeFirestore(app,
{localCache:
persistentLocalCache(/*settings*/{tabManager: persistentSingleTabManager()})
});
// Use multi-tab IndexedDb persistence.
initializeFirestore(app,
{localCache:
persistentLocalCache(/*settings*/{tabManager: persistentMultipleTabManager()})
});
Web namespaced API
firebase.firestore().enablePersistence()
.catch((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
Swift
Note:
This product is not available on watchOS and App Clip targets.
let settings = FirestoreSettings()
// Use memory-only cache
settings.cacheSettings =
MemoryCacheSettings(garbageCollectorSettings: MemoryLRUGCSettings())
// Use persistent disk cache, with 100 MB cache size
settings.cacheSettings = PersistentCacheSettings(sizeBytes: 100 * 1024 * 1024 as NSNumber)
// Any additional options
// ...
// Enable offline data persistence
let db = Firestore.firestore()
db.settings = settings
Objective-C
Note:
This product is not available on watchOS and App Clip targets.
FIRFirestoreSettings *settings = [[FIRFirestoreSettings alloc] init];
// Use memory-only cache
settings.cacheSettings = [[FIRMemoryCacheSettings alloc]
initWithGarbageCollectorSettings:[[FIRMemoryLRUGCSettings alloc] init]];
// Use persistent disk cache (default behavior)
// This example uses 100 MB.
settings.cacheSettings = [[FIRPersistentCacheSettings alloc]
initWithSizeBytes:@(100 * 1024 * 1024)];
// Any additional options
// ...
// Enable offline data persistence
FIRFirestore *db = [FIRFirestore firestore];
db.settings = settings;
Kotlin+KTX
val settings = firestoreSettings {
// Use memory cache
setLocalCacheSettings(memoryCacheSettings {})
// Use persistent disk cache (default)
setLocalCacheSettings(persistentCacheSettings {})
}
db.firestoreSettings = settings
Java
FirebaseFirestoreSettings settings =
new FirebaseFirestoreSettings.Builder(db.getFirestoreSettings())
// Use memory-only cache
.setLocalCacheSettings(MemoryCacheSettings.newBuilder().build())
// Use persistent disk cache (default)
.setLocalCacheSettings(PersistentCacheSettings.newBuilder()
.build())
.build();
db.setFirestoreSettings(settings);
Dart
// Apple and Android
db.settings = const Settings(persistenceEnabled: true);
// Web
await db
.enablePersistence(const PersistenceSettings(synchronizeTabs: true));
When persistence is enabled, Cloud Firestore caches every document
received from the backend for offline access. Cloud Firestore sets a
default threshold for cache size. After exceeding the default,
Cloud Firestore periodically attempts to clean up older, unused
documents. You can configure a different cache size threshold
or disable the clean-up process completely:
Web modular API
import { initializeFirestore, CACHE_SIZE_UNLIMITED } from "firebase/firestore";
const firestoreDb = initializeFirestore(app, {
cacheSizeBytes: CACHE_SIZE_UNLIMITED
});
Web namespaced API
firebase.firestore().settings({
cacheSizeBytes: firebase.firestore.CACHE_SIZE_UNLIMITED
});
Swift
Note:
This product is not available on watchOS and App Clip targets.
// The default cache size threshold is 100 MB. Configure "cacheSizeBytes"
// for a different threshold (minimum 1 MB) or set to "FirestoreCacheSizeUnlimited"
// to disable clean-up.
let settings = Firestore.firestore().settings
// Set cache size to 100 MB
settings.cacheSettings = PersistentCacheSettings(sizeBytes: 100 * 1024 * 1024 as NSNumber)
Firestore.firestore().settings = settings
Objective-C
Note:
This product is not available on watchOS and App Clip targets.
// The default cache size threshold is 100 MB. Configure "cacheSizeBytes"
// for a different threshold (minimum 1 MB) or set to "kFIRFirestoreCacheSizeUnlimited"
// to disable clean-up.
FIRFirestoreSettings *settings = [FIRFirestore firestore].settings;
// Set cache size to 100 MB
settings.cacheSettings =
[[FIRPersistentCacheSettings alloc] initWithSizeBytes:@(100 * 1024 * 1024)];
[FIRFirestore firestore].settings = settings;
Kotlin+KTX
// The default cache size threshold is 100 MB. Configure "setCacheSizeBytes"
// for a different threshold (minimum 1 MB) or set to "CACHE_SIZE_UNLIMITED"
// to disable clean-up.
val settings = FirebaseFirestoreSettings.Builder()
.setCacheSizeBytes(FirebaseFirestoreSettings.CACHE_SIZE_UNLIMITED)
.build()
db.firestoreSettings = settings
Java
// The default cache size threshold is 100 MB. Configure "setCacheSizeBytes"
// for a different threshold (minimum 1 MB) or set to "CACHE_SIZE_UNLIMITED"
// to disable clean-up.
FirebaseFirestoreSettings settings = new FirebaseFirestoreSettings.Builder()
.setCacheSizeBytes(FirebaseFirestoreSettings.CACHE_SIZE_UNLIMITED)
.build();
db.setFirestoreSettings(settings);
Dart
db.settings = const Settings(
persistenceEnabled: true,
cacheSizeBytes: Settings.CACHE_SIZE_UNLIMITED,
);
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.
Web modular API
import { collection, onSnapshot, where, query } from "firebase/firestore";
const q = query(collection(db, "cities"), where("state", "==", "CA"));
onSnapshot(q, { includeMetadataChanges: true }, (snapshot) => {
snapshot.docChanges().forEach((change) => {
if (change.type === "added") {
console.log("New city: ", change.doc.data());
}
const source = snapshot.metadata.fromCache ? "local cache" : "server";
console.log("Data came from " + source);
});
});
Web namespaced API
db.collection("cities").where("state", "==", "CA")
.onSnapshot({ includeMetadataChanges: true }, (snapshot) => {
snapshot.docChanges().forEach((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);
});
});
Swift
Note:
This product is not available on watchOS and App Clip targets.
// 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)")
}
Objective-C
Note:
This product is not available on watchOS and App Clip targets.
// 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);
}];
Kotlin+KTX
db.collection("cities").whereEqualTo("state", "CA")
.addSnapshotListener(MetadataChanges.INCLUDE) { querySnapshot, e ->
if (e != null) {
Log.w(TAG, "Listen error", e)
return@addSnapshotListener
}
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")
}
}
Java
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);
}
}
});
Dart
db
.collection("cities")
.where("state", isEqualTo: "CA")
.snapshots(includeMetadataChanges: true)
.listen((querySnapshot) {
for (var change in querySnapshot.docChanges) {
if (change.type == DocumentChangeType.added) {
final source =
(querySnapshot.metadata.isFromCache) ? "local cache" : "server";
print("Data fetched from $source}");
}
}
});
Get offline data
If you get a document while the device is offline, Cloud Firestore
returns data from the cache.
When querying a collection, an empty result is returned if there are no cached
documents. When fetching a specific document, an error is returned instead.
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.
By default, the Firestore SDK scans all documents in a collection in its
local cache when executing offline queries. With this default behavior, offline
query performance can suffer when users are offline for long periods of time.
With persistent cache enabled, you can improve the performance of offline
queries by allowing the SDK to create local query indexes automatically.
Automatic indexing is disabled by default. Your app must enable
automatic indexing each time it starts. Control whether automatic indexing is
enabled as shown below.
Swift
if let indexManager = Firestore.firestore().persistentCacheIndexManager {
// Indexing is disabled by default
indexManager.enableIndexAutoCreation()
} else {
print("indexManager is nil")
}
Objective-C
PersistentCacheIndexManager *indexManager = [FIRFirestore firestore].persistentCacheIndexManager;
if (indexManager) {
// Indexing is disabled by default
[indexManager enableIndexAutoCreation];
}
Kotlin+KTX
// return type: PersistentCacheManager?
Firebase.firestore.persistentCacheIndexManager?.apply {
// Indexing is disabled by default
enableIndexAutoCreation()
} ?: println("indexManager is null")
Java
// return type: @Nullable PersistentCacheIndexManager
PersistentCacheIndexManager indexManager = FirebaseFirestore.getInstance().getPersistentCacheIndexManager();
if (indexManager != null) {
// Indexing is disabled by default
indexManager.enableIndexAutoCreation();
}
// If not check indexManager != null, IDE shows warning: Method invocation 'enableIndexAutoCreation' may produce 'NullPointerException'
FirebaseFirestore.getInstance().getPersistentCacheIndexManager().enableIndexAutoCreation();
Once automatic indexing is enabled, the SDK evaluates which collections have
a large number of cached documents and optimizes performance of local queries.
The SDK provides a method for deleting query indexes.
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.
Web modular API
import { disableNetwork } from "firebase/firestore";
await disableNetwork(db);
console.log("Network disabled!");
// Do offline actions
// ...
Web namespaced API
firebase.firestore().disableNetwork()
.then(() => {
// Do offline actions
// ...
});
Swift
Note:
This product is not available on watchOS and App Clip targets.
Firestore.firestore().disableNetwork { (error) in
// Do offline things
// ...
}
Objective-C
Note:
This product is not available on watchOS and App Clip targets.
[[FIRFirestore firestore] disableNetworkWithCompletion:^(NSError *_Nullable error) {
// Do offline actions
// ...
}];
Kotlin+KTX
db.disableNetwork().addOnCompleteListener {
// Do offline things
// ...
}
Java
db.disableNetwork()
.addOnCompleteListener(new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
// Do offline things
// ...
}
});
Dart
db.disableNetwork().then((_) {
// Do offline things
});
Use the following method to re-enable network access:
Web modular API
import { enableNetwork } from "firebase/firestore";
await enableNetwork(db);
// Do online actions
// ...
Web namespaced API
firebase.firestore().enableNetwork()
.then(() => {
// Do online actions
// ...
});
Swift
Note:
This product is not available on watchOS and App Clip targets.
Firestore.firestore().enableNetwork { (error) in
// Do online things
// ...
}
Objective-C
Note:
This product is not available on watchOS and App Clip targets.
[[FIRFirestore firestore] enableNetworkWithCompletion:^(NSError *_Nullable error) {
// Do online actions
// ...
}];
Kotlin+KTX
db.enableNetwork().addOnCompleteListener {
// Do online things
// ...
}
Java
db.enableNetwork()
.addOnCompleteListener(new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
// Do online things
// ...
}
});
Dart
db.enableNetwork().then((_) {
// Back online
});