What is Local Storage?
TL;DR
Browser storage API for persisting data indefinitely with no expiration date, shared across all tabs.
Local Storage is a web storage API that persists data indefinitely in the browser with no expiration date. Data is shared across all tabs and windows of the same origin, making it ideal for user preferences and settings.
Local Storage API:
localStorage.setItem('theme', 'dark');
const theme = localStorage.getItem('theme');
localStorage.removeItem('theme');
localStorage.clear();
Common use cases:
- User preferences: Theme, language, layout settings
- Authentication tokens: Store JWTs for persistent login
- Form drafts: Save form progress across sessions
- Feature flags: Store user-specific feature toggles
- Analytics: Track user behavior across visits
Local Storage vs Session Storage:
- Local: Persists forever, shared across tabs
- Session: Cleared on tab close, isolated per tab
Storage limits:
- Most browsers: 5-10MB per origin
- Synchronous API: Can block main thread on large operations
- String Only: Must serialize objects to JSON
Key benefits:
- Persistent: Data survives browser restarts
- Simple API: Easy key-value storage
- No server: Reduces server load for user preferences
- Fast access: No network latency
AI-Friendly: Local Storage uses a straightforward key-value API that AI can implement easily. AI can generate type-safe wrappers, handle serialization, manage storage quotas, and suggest appropriate data for local vs server storage.