Cookies vs Web Storage

Cookies are sent to the server with every HTTP request. Web Storage stays client-side only. Use cookies for server-visible state (sessions, auth tokens) and Storage for UI preferences.

Example

// Cookies: sent with every request to the server
document.cookie = "sessionId=abc; Secure; HttpOnly; SameSite=Strict";

// localStorage: client-side only, never sent to server
localStorage.setItem("theme", "dark");

// Key differences:
// Cookies: 4KB limit, server access, expiry dates
// localStorage: 5MB limit, JS-only, no expiry
// sessionStorage: 5MB limit, JS-only, per-tab

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Pro Tip

Use HttpOnly cookies for auth tokens — JavaScript cannot access them, protecting against XSS attacks.

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