IndexedDB vs. LocalStorage: Choosing Client-Side Databases for Web Apps

The Client Storage Limit

Building responsive offline-capable web applications requires storing data directly in the user's browser. While simple strings can be saved in LocalStorage, caching large datasets requires transactional databases.

We evaluate the structural differences between LocalStorage and IndexedDB in late 2014.

Storage Rule: Use LocalStorage only for lightweight configuration preferences. Use IndexedDB for transactional database caches.

LocalStorage: Synchronous Simplicity

LocalStorage is a simple key-value store:

• ◆Pros: Trivial API syntax (localStorage.setItem('key', 'val')).
• ◆Cons: Synchronous execution blocks the main browser thread. Storage size is limited to 5MB, and it only supports strings.

IndexedDB: Transactional Asynchrony

IndexedDB is an object-oriented, transactional database:

• ◆Pros: Asynchronous execution keeps UI threads responsive. Supports object serialization (indexes, cursors, binary files) and handles large storage capacities (50MB+).
• ◆Cons: Complex, callback-driven API syntax.

Implementing IndexedDB Operations

// Opening a transactional database in early 2014 IndexedDB
const request = indexedDB.open("SchoolDatabase", 1);

request.onupgradeneeded = function(event) {
    const db = event.target.result;
    const objectStore = db.createObjectStore("students", { keyPath: "id" });
    objectStore.createIndex("name", "name", { unique: false });
};

By adopting IndexedDB, developers build web applications that perform complex database queries offline, maintaining UI responsiveness.