What is IndexedDB
Key idea:
IndexedDB — a browser-built-in NoSQL database storing structured data (records, blobs, files) on the client. Async API, transactional, supports indexes, 100+ MB storage. Used in PWAs for offline-first + large-volume cache. Replaces deprecated WebSQL. Alternatives: localForage (wrapper), Dexie.js (ORM-like).
Below: details, example, related terms, FAQ.
Details
- Object stores (= collections): organize records by keyPath
- Transactions: readonly / readwrite / versionchange
- Indexes: secondary keys for efficient queries
- Storage quota: ~20-60% of free disk (Chrome), ~1GB (Safari)
- Eviction: browser may clear when space is low
Example
const request = indexedDB.open('myDB', 1);
request.onupgradeneeded = e => {
e.target.result.createObjectStore('users', { keyPath: 'id' });
};
request.onsuccess = e => {
const tx = e.target.result.transaction('users', 'readwrite');
tx.objectStore('users').put({ id: 1, name: 'Alice' });
};Related Terms
Learn more
Frequently Asked Questions
IndexedDB vs localStorage?
localStorage — 5-10 MB, sync, string-only. IndexedDB — gigabytes, async, structured objects + indexes.
Mobile support?
Yes, every modern browser (Safari iOS, Chrome Android). Safari is partially limited in PWA context.
Eviction — will my data disappear?
When disk space is tight — yes. For critical data use <code>navigator.storage.persist()</code>.