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# Directives
## React Directives
These are React directives, not Next.js specific.
### `'use client'`
Marks a component as a Client Component. Required for:
- React hooks (`useState`, `useEffect`, etc.)
- Event handlers (`onClick`, `onChange`)
- Browser APIs (`window`, `localStorage`)
```tsx
'use client';
import { useState } from 'react';
export function Counter() {
const [count, setCount] = useState(0);
return <button onClick={() => setCount(count + 1)}>{count}</button>;
}
```
Reference: https://react.dev/reference/rsc/use-client
### `'use server'`
Marks a function as a Server Action. Can be passed to Client Components.
```tsx
'use server';
export async function submitForm(formData: FormData) {
// Runs on server
}
```
Or inline within a Server Component:
```tsx
export default function Page() {
async function submit() {
'use server';
// Runs on server
}
return <form action={submit}>...</form>;
}
```
Reference: https://react.dev/reference/rsc/use-server
---
## Next.js Directive
### `'use cache'`
Marks a function or component for caching. Part of Next.js Cache Components.
```tsx
'use cache';
export async function getCachedData() {
return await fetchData();
}
```
Requires `cacheComponents: true` in `next.config.ts`.
For detailed usage including cache profiles, `cacheLife()`, `cacheTag()`, and `updateTag()`, see the `next-cache-components` skill.
Reference: https://nextjs.org/docs/app/api-reference/directives/use-cache