# Source: https://nextjs.org/docs/app/api-reference/directives/use-server.md

# use server
@doc-version: 16.0.4


The `use server` directive designates a function or file to be executed on the **server side**. It can be used at the top of a file to indicate that all functions in the file are server-side, or inline at the top of a function to mark the function as a [Server Function](https://19.react.dev/reference/rsc/server-functions). This is a React feature.

## Using `use server` at the top of a file

The following example shows a file with a `use server` directive at the top. All functions in the file are executed on the server.

```tsx filename="app/actions.ts" highlight={1} switcher
'use server'
import { db } from '@/lib/db' // Your database client

export async function createUser(data: { name: string; email: string }) {
  const user = await db.user.create({ data })
  return user
}
```

```jsx filename="app/actions.js" highlight={1} switcher
'use server'
import { db } from '@/lib/db' // Your database client

export async function createUser(data) {
  const user = await db.user.create({ data })
  return user
}
```

### Using Server Functions in a Client Component

To use Server Functions in Client Components you need to create your Server Functions in a dedicated file using the `use server` directive at the top of the file. These Server Functions can then be imported into Client and Server Components and executed.

Assuming you have a `fetchUsers` Server Function in `actions.ts`:

```tsx filename="app/actions.ts" highlight={1} switcher
'use server'
import { db } from '@/lib/db' // Your database client

export async function fetchUsers() {
  const users = await db.user.findMany()
  return users
}
```

```jsx filename="app/actions.js" highlight={1} switcher
'use server'
import { db } from '@/lib/db' // Your database client

export async function fetchUsers() {
  const users = await db.user.findMany()
  return users
}
```

Then you can import the `fetchUsers` Server Function into a Client Component and execute it on the client-side.

```tsx filename="app/components/my-button.tsx" highlight={1,2,8} switcher
'use client'
import { fetchUsers } from '../actions'

export default function MyButton() {
  return <button onClick={() => fetchUsers()}>Fetch Users</button>
}
```

```jsx filename="app/components/my-button.js" highlight={1,2,8} switcher
'use client'
import { fetchUsers } from '../actions'

export default function MyButton() {
  return <button onClick={() => fetchUsers()}>Fetch Users</button>
}
```

## Using `use server` inline

In the following example, `use server` is used inline at the top of a function to mark it as a [Server Function](https://19.react.dev/reference/rsc/server-functions):

```tsx filename="app/posts/[id]/page.tsx" switcher highlight={8}
import { EditPost } from './edit-post'
import { revalidatePath } from 'next/cache'

export default async function PostPage({ params }: { params: { id: string } }) {
  const post = await getPost(params.id)

  async function updatePost(formData: FormData) {
    'use server'
    await savePost(params.id, formData)
    revalidatePath(`/posts/${params.id}`)
  }

  return <EditPost updatePostAction={updatePost} post={post} />
}
```

```jsx filename="app/posts/[id]/page.js" switcher highlight={8}
import { EditPost } from './edit-post'
import { revalidatePath } from 'next/cache'

export default async function PostPage({ params }) {
  const post = await getPost(params.id)

  async function updatePost(formData) {
    'use server'
    await savePost(params.id, formData)
    revalidatePath(`/posts/${params.id}`)
  }

  return <EditPost updatePostAction={updatePost} post={post} />
}
```

## Security considerations

When using the `use server` directive, it's important to ensure that all server-side logic is secure and that sensitive data remains protected.

### Authentication and authorization

Always authenticate and authorize users before performing sensitive server-side operations.

```tsx filename="app/actions.ts" highlight={1,7,8,9,10} switcher
'use server'

import { db } from '@/lib/db' // Your database client
import { authenticate } from '@/lib/auth' // Your authentication library

export async function createUser(
  data: { name: string; email: string },
  token: string
) {
  const user = authenticate(token)
  if (!user) {
    throw new Error('Unauthorized')
  }
  const newUser = await db.user.create({ data })
  return newUser
}
```

```jsx filename="app/actions.js" highlight={1,7,8,9,10} switcher
'use server'

import { db } from '@/lib/db' // Your database client
import { authenticate } from '@/lib/auth' // Your authentication library

export async function createUser(data, token) {
  const user = authenticate(token)
  if (!user) {
    throw new Error('Unauthorized')
  }
  const newUser = await db.user.create({ data })
  return newUser
}
```

## Reference

See the [React documentation](https://react.dev/reference/rsc/use-server) for more information on `use server`.