---
title: Mutating Data
description: Learn how to mutate data using Server Functions and Server Actions in Next.js.
related:
  title: API Reference
  description: Learn more about the features mentioned in this page by reading the API Reference.
  links:
    - app/api-reference/functions/revalidatePath
    - app/api-reference/functions/revalidateTag
    - app/api-reference/functions/redirect
---

You can mutate data in Next.js using [React Server Functions](https://react.dev/reference/rsc/server-functions). This page will go through how you can [create](#creating-server-functions) and [invoke](#invoking-server-functions) Server Functions.

## What are Server Functions?

A **Server Function** is an asynchronous function that runs on the server. You can call them from the client through a network request, which is why they must be asynchronous.

In an `action` or mutation context, they are also called **Server Actions**.

By convention, a Server Action is an async function used with [`startTransition`](https://react.dev/reference/react/startTransition). This happens automatically when the function is:

- Passed to a `<form>` using the `action` prop.
- Passed to a `<button>` using the `formAction` prop.

When an action is invoked, Next.js can return both the updated UI and new data in a single server roundtrip.

Behind the scenes, actions use the `POST` method, and only this HTTP method can invoke them.

> [!WARNING]
> Server Functions are reachable via direct POST requests, not just through your application's UI. Always verify authentication and authorization inside every Server Function. See the [Data Security guide](/docs/app/guides/data-security#authentication-and-authorization) for recommended patterns.

> **Good to know:** A Server Action is a Server Function used in a specific way (for handling form submissions and mutations). Server Function is the broader term.

## Creating Server Functions

A Server Function can be defined by using the [`use server`](https://react.dev/reference/rsc/use-server) directive. You can place the directive at the top of an **asynchronous** function to mark the function as a Server Function, or at the top of a separate file to mark all exports of that file.

```ts filename="app/lib/actions.ts" switcher
import { auth } from '@/lib/auth'

export async function createPost(formData: FormData) {
  'use server'
  const session = await auth()
  if (!session?.user) {
    throw new Error('Unauthorized')
  }

  const title = formData.get('title')
  const content = formData.get('content')

  // Mutate data
  // Revalidate cache
}

export async function deletePost(formData: FormData) {
  'use server'
  const session = await auth()
  if (!session?.user) {
    throw new Error('Unauthorized')
  }

  const id = formData.get('id')

  // Verify the user owns this resource before deleting
  // Mutate data
  // Revalidate cache
}
```

```js filename="app/lib/actions.js" switcher
import { auth } from '@/lib/auth'

export async function createPost(formData) {
  'use server'
  const session = await auth()
  if (!session?.user) {
    throw new Error('Unauthorized')
  }

  const title = formData.get('title')
  const content = formData.get('content')

  // Mutate data
  // Revalidate cache
}

export async function deletePost(formData) {
  'use server'
  const session = await auth()
  if (!session?.user) {
    throw new Error('Unauthorized')
  }

  const id = formData.get('id')

  // Verify the user owns this resource before deleting
  // Mutate data
  // Revalidate cache
}
```

### Server Components

Server Functions can be inlined in Server Components by adding the `"use server"` directive to the top of the function body:

```tsx filename="app/page.tsx" switcher
export default function Page() {
  // Server Action
  async function createPost(formData: FormData) {
    'use server'
    // ...
  }

  return <></>
}
```

```jsx filename="app/page.js" switcher
export default function Page() {
  // Server Action
  async function createPost(formData) {
    'use server'
    // ...
  }

  return <></>
}
```

> **Good to know:** Server Components support progressive enhancement by default, meaning forms that call Server Actions will be submitted even if JavaScript hasn't loaded yet or is disabled.

### Client Components

It's not possible to define Server Functions in Client Components. However, you can invoke them in Client Components by importing them from a file that has the `"use server"` directive at the top of it:

```ts filename="app/actions.ts" switcher
'use server'

export async function createPost() {}
```

```js filename="app/actions.js" switcher
'use server'

export async function createPost() {}
```

```tsx filename="app/ui/button.tsx" switcher
'use client'

import { createPost } from '@/app/actions'

export function Button() {
  return <button formAction={createPost}>Create</button>
}
```

```jsx filename="app/ui/button.js" switcher
'use client'

import { createPost } from '@/app/actions'

export function Button() {
  return <button formAction={createPost}>Create</button>
}
```

> **Good to know:** In Client Components, forms invoking Server Actions will queue submissions if JavaScript isn't loaded yet, and will be prioritized for hydration. After hydration, the browser does not refresh on form submission.

### Passing actions as props

You can also pass an action to a Client Component as a prop:

```jsx
<ClientComponent updateItemAction={updateItem} />
```

```tsx filename="app/client-component.tsx" switcher
'use client'

export default function ClientComponent({
  updateItemAction,
}: {
  updateItemAction: (formData: FormData) => void
}) {
  return <form action={updateItemAction}>{/* ... */}</form>
}
```

```jsx filename="app/client-component.js" switcher
'use client'

export default function ClientComponent({ updateItemAction }) {
  return <form action={updateItemAction}>{/* ... */}</form>
}
```

## Invoking Server Functions

There are two main ways you can invoke a Server Function:

1. [Forms](#forms) in Server and Client Components
2. [Event Handlers](#event-handlers) and [useEffect](#useeffect) in Client Components

> **Good to know:** Server Functions are designed for server-side mutations. The client currently dispatches and awaits them one at a time. This is an implementation detail and may change. If you need parallel data fetching, use [data fetching](/docs/app/getting-started/fetching-data#server-components) in Server Components, or perform parallel work inside a single Server Function or [Route Handler](/docs/app/guides/backend-for-frontend#manipulating-data).

### Forms

React extends the HTML [`<form>`](https://react.dev/reference/react-dom/components/form) element to allow a Server Function to be invoked with the HTML `action` prop.

When invoked in a form, the function automatically receives the [`FormData`](https://developer.mozilla.org/docs/Web/API/FormData/FormData) object. You can extract the data using the native [`FormData` methods](https://developer.mozilla.org/en-US/docs/Web/API/FormData#instance_methods):

```tsx filename="app/ui/form.tsx" switcher
import { createPost } from '@/app/actions'

export function Form() {
  return (
    <form action={createPost}>
      <input type="text" name="title" />
      <input type="text" name="content" />
      <button type="submit">Create</button>
    </form>
  )
}
```

```jsx filename="app/ui/form.js" switcher
import { createPost } from '@/app/actions'

export function Form() {
  return (
    <form action={createPost}>
      <input type="text" name="title" />
      <input type="text" name="content" />
      <button type="submit">Create</button>
    </form>
  )
}
```

```ts filename="app/actions.ts" switcher
'use server'

import { auth } from '@/lib/auth'

export async function createPost(formData: FormData) {
  const session = await auth()
  if (!session?.user) {
    throw new Error('Unauthorized')
  }

  const title = formData.get('title')
  const content = formData.get('content')

  // Mutate data
  // Revalidate cache
}
```

```js filename="app/actions.js" switcher
'use server'

import { auth } from '@/lib/auth'

export async function createPost(formData) {
  const session = await auth()
  if (!session?.user) {
    throw new Error('Unauthorized')
  }

  const title = formData.get('title')
  const content = formData.get('content')

  // Mutate data
  // Revalidate cache
}
```

### Event Handlers

You can invoke a Server Function in a Client Component by using event handlers such as `onClick`.

```tsx filename="app/like-button.tsx" switcher
'use client'

import { incrementLike } from './actions'
import { useState } from 'react'

export default function LikeButton({ initialLikes }: { initialLikes: number }) {
  const [likes, setLikes] = useState(initialLikes)

  return (
    <>
      <p>Total Likes: {likes}</p>
      <button
        onClick={async () => {
          const updatedLikes = await incrementLike()
          setLikes(updatedLikes)
        }}
      >
        Like
      </button>
    </>
  )
}
```

```jsx filename="app/like-button.js" switcher
'use client'

import { incrementLike } from './actions'
import { useState } from 'react'

export default function LikeButton({ initialLikes }) {
  const [likes, setLikes] = useState(initialLikes)

  return (
    <>
      <p>Total Likes: {likes}</p>
      <button
        onClick={async () => {
          const updatedLikes = await incrementLike()
          setLikes(updatedLikes)
        }}
      >
        Like
      </button>
    </>
  )
}
```

## Examples

### Showing a pending state

While executing a Server Function, you can show a loading indicator with React's [`useActionState`](https://react.dev/reference/react/useActionState) hook. This hook returns a `pending` boolean:

```tsx filename="app/ui/button.tsx" switcher
'use client'

import { useActionState, startTransition } from 'react'
import { createPost } from '@/app/actions'
import { LoadingSpinner } from '@/app/ui/loading-spinner'

export function Button() {
  const [state, action, pending] = useActionState(createPost, false)

  return (
    <button onClick={() => startTransition(action)}>
      {pending ? <LoadingSpinner /> : 'Create Post'}
    </button>
  )
}
```

```jsx filename="app/ui/button.js" switcher
'use client'

import { useActionState, startTransition } from 'react'
import { createPost } from '@/app/actions'
import { LoadingSpinner } from '@/app/ui/loading-spinner'

export function Button() {
  const [state, action, pending] = useActionState(createPost, false)

  return (
    <button onClick={() => startTransition(action)}>
      {pending ? <LoadingSpinner /> : 'Create Post'}
    </button>
  )
}
```

### Refresh data

After a mutation, you may want to refresh the current page to show the latest data. You can do this by calling [`refresh`](/docs/app/api-reference/functions/refresh) from `next/cache` in a Server Action:

```ts filename="app/lib/actions.ts" switcher
'use server'

import { auth } from '@/lib/auth'
import { refresh } from 'next/cache'

export async function updatePost(formData: FormData) {
  const session = await auth()
  if (!session?.user) {
    throw new Error('Unauthorized')
  }
  // Mutate data
  // ...

  refresh()
}
```

```js filename="app/lib/actions.js" switcher
'use server'

import { auth } from '@/lib/auth'
import { refresh } from 'next/cache'

export async function updatePost(formData) {
  const session = await auth()
  if (!session?.user) {
    throw new Error('Unauthorized')
  }
  // Mutate data
  // ...

  refresh()
}
```

This refreshes the client router, ensuring the UI reflects the latest state. The `refresh()` function does not revalidate tagged data. To revalidate tagged data, use [`updateTag`](/docs/app/api-reference/functions/updateTag) or [`revalidateTag`](/docs/app/api-reference/functions/revalidateTag) instead.

### Revalidate data

After performing a mutation, you can revalidate the Next.js cache and show the updated data by calling [`revalidatePath`](/docs/app/api-reference/functions/revalidatePath) or [`revalidateTag`](/docs/app/api-reference/functions/revalidateTag) within the Server Function:

```ts filename="app/lib/actions.ts" switcher
import { auth } from '@/lib/auth'
import { revalidatePath } from 'next/cache'

export async function createPost(formData: FormData) {
  'use server'
  const session = await auth()
  if (!session?.user) {
    throw new Error('Unauthorized')
  }
  // Mutate data
  // ...

  revalidatePath('/posts')
}
```

```js filename="app/actions.js" switcher
import { auth } from '@/lib/auth'
import { revalidatePath } from 'next/cache'

export async function createPost(formData) {
  'use server'
  const session = await auth()
  if (!session?.user) {
    throw new Error('Unauthorized')
  }
  // Mutate data
  // ...
  revalidatePath('/posts')
}
```

### Redirect after a mutation

You may want to redirect the user to a different page after a mutation. You can do this by calling [`redirect`](/docs/app/api-reference/functions/redirect) within the Server Function.

```ts filename="app/lib/actions.ts" switcher
'use server'

import { auth } from '@/lib/auth'
import { revalidatePath } from 'next/cache'
import { redirect } from 'next/navigation'

export async function createPost(formData: FormData) {
  const session = await auth()
  if (!session?.user) {
    throw new Error('Unauthorized')
  }
  // Mutate data
  // ...

  revalidatePath('/posts')
  redirect('/posts')
}
```

```js filename="app/actions.js" switcher
'use server'

import { auth } from '@/lib/auth'
import { revalidatePath } from 'next/cache'
import { redirect } from 'next/navigation'

export async function createPost(formData) {
  const session = await auth()
  if (!session?.user) {
    throw new Error('Unauthorized')
  }
  // Mutate data
  // ...

  revalidatePath('/posts')
  redirect('/posts')
}
```

Calling `redirect` [throws](/docs/app/api-reference/functions/redirect#behavior) a framework handled control-flow exception. Any code after it won't execute. If you need fresh data, call [`revalidatePath`](/docs/app/api-reference/functions/revalidatePath) or [`revalidateTag`](/docs/app/api-reference/functions/revalidateTag) beforehand.

### Cookies

You can `get`, `set`, and `delete` cookies inside a Server Action using the [`cookies`](/docs/app/api-reference/functions/cookies) API.

When you [set or delete](/docs/app/api-reference/functions/cookies#understanding-cookie-behavior-in-server-functions) a cookie in a Server Action, Next.js re-renders the current page and its layouts on the server so the **UI reflects the new cookie value**.

> **Good to know**: The server update applies to the current React tree, re-rendering, mounting, or unmounting components, as needed. Client state is preserved for re-rendered components, and effects re-run if their dependencies changed.

```ts filename="app/actions.ts" switcher
'use server'

import { cookies } from 'next/headers'

export async function exampleAction() {
  const cookieStore = await cookies()

  // Get cookie
  cookieStore.get('name')?.value

  // Set cookie
  cookieStore.set('name', 'Delba')

  // Delete cookie
  cookieStore.delete('name')
}
```

```js filename="app/actions.js" switcher
'use server'

import { cookies } from 'next/headers'

export async function exampleAction() {
  // Get cookie
  const cookieStore = await cookies()

  // Get cookie
  cookieStore.get('name')?.value

  // Set cookie
  cookieStore.set('name', 'Delba')

  // Delete cookie
  cookieStore.delete('name')
}
```

### useEffect

You can use the React [`useEffect`](https://react.dev/reference/react/useEffect) hook to invoke a Server Action when the component mounts or a dependency changes. This is useful for mutations that depend on global events or need to be triggered automatically. For example, `onKeyDown` for app shortcuts, an intersection observer hook for infinite scrolling, or when the component mounts to update a view count:

```tsx filename="app/view-count.tsx" switcher
'use client'

import { incrementViews } from './actions'
import { useState, useEffect, useTransition } from 'react'

export default function ViewCount({ initialViews }: { initialViews: number }) {
  const [views, setViews] = useState(initialViews)
  const [isPending, startTransition] = useTransition()

  useEffect(() => {
    startTransition(async () => {
      const updatedViews = await incrementViews()
      setViews(updatedViews)
    })
  }, [])

  // You can use `isPending` to give users feedback
  return <p>Total Views: {views}</p>
}
```

```jsx filename="app/view-count.js" switcher
'use client'

import { incrementViews } from './actions'
import { useState, useEffect, useTransition } from 'react'

export default function ViewCount({ initialViews }) {
  const [views, setViews] = useState(initialViews)
  const [isPending, startTransition] = useTransition()

  useEffect(() => {
    startTransition(async () => {
      const updatedViews = await incrementViews()
      setViews(updatedViews)
    })
  }, [])

  // You can use `isPending` to give users feedback
  return <p>Total Views: {views}</p>
}
```