localStorage stores data permanently in the browser. sessionStorage clears when the tab closes. Both store strings — use JSON.stringify and JSON.parse for objects. IndexedDB handles larger structured data needs.
Web Storage APIs
// localStorage — persists across sessions
localStorage.setItem("theme", "dark");
const theme = localStorage.getItem("theme");
localStorage.removeItem("theme");
localStorage.clear();
// sessionStorage — clears when tab closes
sessionStorage.setItem("token", "abc123");
// IndexedDB — for large structured data
// Use a library like idb or Dexie.js