Firestore web errorFirestore: “Failed to obtain exclusive access to the persistence layer”

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Why the second tab can’t get the cache, and the fix

1. 01

   The app uses single-tab persistence

   “Defaults to single-tab persistence if no tab manager is specified.” Firebase, Access data offline (web)

   persistentLocalCache with no tab manager is single-tab. The second tab keeps working, but without offline data, and its cache isn’t shared. Pass persistentMultipleTabManager so all tabs share the cache.

   import { initializeFirestore, persistentLocalCache, persistentMultipleTabManager } from 'firebase/firestore';
   
   const db = initializeFirestore(app, {
     localCache: persistentLocalCache({ tabManager: persistentMultipleTabManager() }),
   });

2. 02

   The code still calls enableIndexedDbPersistence

   “The app is already open in another browser tab.” Firebase, enableIndexedDbPersistence (failed-precondition)

   The older call is single-tab and rejects with failed-precondition when the app is already open in another tab. Firebase marks it obsolete; move to localCache in initializeFirestore.

3. 03

   Old and new settings are mixed

   “Calling this function when FirestoreSettings.localCache is already specified will throw an exception.” Firebase, enableIndexedDbPersistence

   Calling enableIndexedDbPersistence or enableMultiTabIndexedDbPersistence after setting localCache throws. Keep only the localCache setting.

4. 04

   Tabs use different persistence settings

   Also check: the full message mentions experimentalForceOwningTab, the older option that makes one tab take the cache without checking (persistentSingleTabManager with forceOwnership in the new API). With it, only one tab may have persistence on at a time. Remove it and use persistentMultipleTabManager in every tab.

Checked against the vendor’s docs on November 9, 2026: Firebase docs: Access data offline; Firebase JS reference: firestore.

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Related: Firestore client is offline · Firestore deadline exceeded · Firestore quota exceeded · Cloud Firestore API disabled