Solving Hydration Errors in Next.js

Hydration errors happen when server-rendered markup doesn’t match the client-rendered markup.

Common Causes

Using `Math.random()`, `Date.now()`, or browser APIs like `window` or `navigator` during render.

Timezone differences when rendering dates.

Before:

{Date.now()}

After:

'use client';
const [now, setNow] = useState('');

useEffect(() => {
  setNow(new Date().toISOString());
}, []);

return {now};

Avoid dynamic content on the server.

Use effects/hooks for browser-specific logic.

Wrap conditional rendering with `typeof window !== 'undefined'`.

Fixing hydration issues improves your app’s stability and SSR experience.