Browser Storage Explained: LocalStorage vs SessionStorage vs IndexedDB vs Cookies

Browsers offer four distinct storage mechanisms, each designed for different scenarios. LocalStorage provides persistent key-value storage (5–10 MB) that survives browser restarts — ideal for user preferences and cached data. SessionStorage is identical in API but scoped to a single tab/session, perfect for temporary form data.

IndexedDB is an asynchronous, transactional database supporting structured data, indexes, and gigabytes of storage — use it for offline-first apps and large datasets. Cookies are the oldest mechanism (4 KB limit) but uniquely sent with every HTTP request, making them essential for authentication tokens and server-side sessions.

Key decision factors: persistence needs, data size, whether the server needs access, and sync vs async requirements. Choosing the wrong storage type leads to performance issues, security vulnerabilities, or poor user experience.