The Storage Standard defines an API for persistent storage and quota estimates, and the platform storage architecture. We're launching an API for making persistent storage eviction under heavy memory pressure more predictable. It's available as of Chromium 122.
What problem does the storage standard solve?
Traditionally, as the user runs out of storage space on their device, the data stored with APIs like
IndexedDB or localStorage
gets lost without the user being able to intervene. A way to make
storage persistent is through invoking the
persist()
method of the
StorageManager
interface. It simultaneously requests the end user for permission and changes the
storage to be persistent once granted:
const persisted = await navigator.storage.persist();
if (persisted) {
/* Storage will not be cleared except by explicit user action. */
}
This method of asking for storage to be persisted is all or nothing. There's no way to express more fine-grained persistence needs. It's all one storage bucket.
The Storage Buckets API
The core idea of the Storage Buckets API is granting sites the ability to create multiple storage buckets, where the browser may choose to delete each bucket independently of other buckets. This allows developers to specify eviction prioritization to make sure the most valuable data doesn't get deleted.
Use case example
To illustrate where storage buckets would come in handy, imagine an email application. It would be unforgivable if the app lost the user's unsent drafts that only exist on the client. In contrast, if they are stored on a server, the user would probably be fine with some of their oldest inbox emails to be removed from the client if their browser is under heavy storage pressure.
Use the Storage Buckets API
Create a new storage bucket
A new storage bucket can be created with the open()
method on the StorageBucketManager
interface.
// Create a storage bucket for emails that are synchronized with the
// server.
const inboxBucket = await navigator.storageBuckets.open('inbox');
Create a persisted new storage bucket
To ensure the storage bucket is persisted, you can pass durability
and persisted
option
arguments to the open()
method:
persisted
determines if the storage bucket should be persisted or not. The allowed values are eitherfalse
(default) ortrue
.durability
provides a hint to the browser that helps it trade off write performance against a reduced risk of data loss in the event of power failures. The allowed values are'relaxed'
(default) or'strict'
:'strict'
buckets attempt to minimize the risk of data loss on power failure. This may come at the cost of reduced performance, meaning that writes may take longer to complete, might impact overall system performance, may consume more battery power, and may wear out the storage device faster.'relaxed'
buckets may "forget" writes that were completed in the last few seconds, when a power loss occurs. In return, writing data to these buckets may have better performance characteristics, and may allow a battery charge to last longer, and may result in longer storage device lifetime. Also, power failure won't lead to data corruption at a higher rate than for'strict'
buckets.
// Create a storage bucket for email drafts that only exist on the client.
const draftsBucket = await navigator.storageBuckets.open('drafts', {
durability: 'strict', // Or `'relaxed'`.
persisted: true, // Or `false`.
});
Access the storage APIs from a storage bucket
Each storage bucket is associated with storage APIs, for example,
IndexedDB, the
Cache interface, or the
File interface. These storage APIs work as per
the usual, just that the entry point is from the StorageBucket
interface, for example,
StorageBucket.indexedDB
.
const inboxDb = await new Promise(resolve => {
const request = inboxBucket.indexedDB.open('messages');
request.onupgradeneeded = () => { /* migration code */ };
request.onsuccess = () => resolve(request.result);
request.onerror = () => reject(request.error);
});
Debug storage buckets in DevTools
Inspect storage buckets in a dedicated tree in the Application > Storage section.