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.
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
PersistenceEnabledoption tofalse. - For the web, offline persistence is disabled by default. To enable
persistence, call the
enablePersistencemethod. 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
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
Swift
let settings = FirestoreSettings() settings.isPersistenceEnabled = true // Any additional options // ... // Enable offline data persistence let db = Firestore.firestore() db.settings = settings
Objective-C
FIRFirestoreSettings *settings = [[FIRFirestoreSettings alloc] init]; settings.persistenceEnabled = YES; // Any additional options // ... // Enable offline data persistence FIRFirestore *db = [FIRFirestore firestore]; db.settings = settings;
Java
FirebaseFirestoreSettings settings = new FirebaseFirestoreSettings.Builder()
.setPersistenceEnabled(true)
.build();
db.setFirestoreSettings(settings);
Kotlin
val settings = FirebaseFirestoreSettings.Builder()
.setPersistenceEnabled(true)
.build()
db.firestoreSettings = settings
Configure cache size
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
// The default cache size threshold is 40 MB. Configure "cacheSizeBytes"
// for a different threshold (minimum 1 MB) or set to "CACHE_SIZE_UNLIMITED"
// to disable clean-up.
firebase.firestore().settings({
cacheSizeBytes: firebase.firestore.CACHE_SIZE_UNLIMITED
});
firebase.firestore().enablePersistence()
Swift
// 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 settings.cacheSizeBytes = FirestoreCacheSizeUnlimited Firestore.firestore().settings = settings
Objective-C
// 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; settings.cacheSizeBytes = kFIRFirestoreCacheSizeUnlimited; [FIRFirestore firestore].settings = 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);
Kotlin
// 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
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
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);
});
});
Swift
// 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
// 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);
}];
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);
}
}
});
Kotlin
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")
}
}
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.
Web
firebase.firestore().disableNetwork()
.then(function() {
// Do offline actions
// ...
});
Swift
Firestore.firestore().disableNetwork { (error) in
// Do offline things
// ...
}
Objective-C
[[FIRFirestore firestore] disableNetworkWithCompletion:^(NSError *_Nullable error) {
// Do offline actions
// ...
}];
Java
db.disableNetwork()
.addOnCompleteListener(new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
// Do offline things
// ...
}
});
Kotlin
db.disableNetwork().addOnCompleteListener {
// Do offline things
// ...
}
Use the following method to re-enable network access:
Web
firebase.firestore().enableNetwork()
.then(function() {
// Do online actions
// ...
});
Swift
Firestore.firestore().enableNetwork { (error) in
// Do online things
// ...
}
Objective-C
[[FIRFirestore firestore] enableNetworkWithCompletion:^(NSError *_Nullable error) {
// Do online actions
// ...
}];
Java
db.enableNetwork()
.addOnCompleteListener(new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
// Do online things
// ...
}
});
Kotlin
db.enableNetwork().addOnCompleteListener {
// Do online things
// ...
}