---
title: Field Hooks
label: Fields
order: 40
desc: Hooks can be added to any fields, and optionally modify the return value of the field before the operation continues.
keywords: hooks, fields, config, configuration, documentation, Content Management System, cms, headless, javascript, node, react, nextjs
---

Field Hooks are [Hooks](./overview) that run on Documents on a per-field basis. They allow you to execute your own logic during specific events of the Document lifecycle. Field Hooks offer incredible potential for isolating your logic from the rest of your [Collection Hooks](./collections) and [Global Hooks](./globals).

To add Hooks to a Field, use the `hooks` property in your [Field Config](../fields/overview):

```ts
import type { Field } from 'payload';

export const FieldWithHooks: Field = {
  // ...
  hooks: { // highlight-line
    // ...
  },
}
```

## Config Options

All Field Hooks accept an array of synchronous or asynchronous functions. These functions can optionally modify the return value of the field before the operation continues. All Field Hooks are formatted to accept the same arguments, although some arguments may be `undefined` based the specific hook type.

<Banner type="warning">
  **Important:**
  Due to GraphQL's typed nature, changing the type of data that you return from a field will produce errors in the [GraphQL API](../graphql/overview). If you need to change the shape or type of data, consider [Collection Hooks](./collections) or [Global Hooks](./hooks) instead.
</Banner>

To add hooks to a Field, use the `hooks` property in your [Field Config](../fields/overview):

```ts
import type { Field } from 'payload';

const FieldWithHooks: Field = {
  name: 'name',
  type: 'text',
  // highlight-start
  hooks: {
    beforeValidate: [(args) => {...}],
    beforeChange: [(args) => {...}],
    beforeDuplicate: [(args) => {...}],
    afterChange: [(args) => {...}],
    afterRead: [(args) => {...}],
  }
  // highlight-end
}
```

The following arguments are provided to all Field Hooks:

| Option                   | Description                                                                                                                                                                                                           |
| ------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **`collection`**         | The [Collection](../configuration/collections) in which this Hook is running against. If the field belongs to a Global, this will be `null`.                                                                                                                       |
| **`context`**            | Custom context passed between Hooks. [More details](./context).                                                                                                                              |
| **`data`**               | In the `afterRead` hook this is the full Document. In the `create` and `update` operations, this is the incoming data passed through the operation.                                                                                 |
| **`field`**              | The [Field](../fields/overview) which the Hook is running against.                                                                                                                                                                          |
| **`findMany`**           | Boolean to denote if this hook is running against finding one, or finding many within the `afterRead` hook.                                                                                                           |
| **`global`**             | The [Global](../configuration/globals) in which this Hook is running against. If the field belongs to a Collection, this will be `null`.                                                                                                                       |
| **`operation`**          | The name of the operation that this hook is running within. Useful within `beforeValidate`, `beforeChange`, and `afterChange` hooks to differentiate between `create` and `update` operations. |
| **`originalDoc`**        | In the `update` operation, this is the Document before changes were applied. In the `afterChange` hook, this is the resulting Document.                                                                                        |
| **`overrideAccess`**        | A boolean to denote if the current operation is overriding [Access Control](../access-control/overview).                                                                                                                                                                          |
| **`path`**             | The path to the [Field](../fields/overview) in the schema.                                                                                                                                                                          |
| **`previousDoc`**        | In the `afterChange` Hook, this is the Document before changes were applied.                                                                                                                                                |
| **`previousSiblingDoc`** | The sibling data of the Document before changes being applied, only in `beforeChange` and `afterChange` hook.                                                                                                         |
| **`previousValue`**      | The previous value of the field, before changes, only in `beforeChange` and `afterChange` hooks.                                                                                                                      |
| **`req`**                | The [Web Request](https://developer.mozilla.org/en-US/docs/Web/API/Request) object. This is mocked for [Local API](../local-api/overview) operations.                                                                                                                                                  |
| **`schemaPath`**         | The path of the [Field](../fields/overview) in the schema.                                                                                                                                                                                  |
| **`siblingData`**        | The data of sibling fields adjacent to the field that the Hook is running against.        |
| **`siblingDocWithLocales`**      | The sibling data of the Document with all [Locales](../configuration/localization).        |
| **`value`**              | The value of the [Field](../fields/overview).                                                                                                                                                                                               |

<Banner type="success">
  **Tip:**
  It's a good idea to conditionally scope your logic based on which operation is executing. For example, if you are writing a `beforeChange` hook, you may want to perform different logic based on if the current `operation` is `create` or `update`.
</Banner>

### beforeValidate

Runs before the `update` operation. This hook allows you to pre-process or format field data before it undergoes validation.

```ts
import type { Field } from 'payload'

const usernameField: Field = {
  name: 'username',
  type: 'text',
  hooks: {
    beforeValidate: [
      ({ value }) => {
        // Trim whitespace and convert to lowercase
        return value.trim().toLowerCase()
      },
    ],
  },
}
```

In this example, the `beforeValidate` hook is used to process the `username` field. The hook takes the incoming value of
the field and transforms it by trimming whitespace and converting it to lowercase. This ensures that the username is
stored in a consistent format in the database.

### beforeChange

Immediately following validation, `beforeChange` hooks will run within `create` and `update` operations. At this stage,
you can be confident that the field data that will be saved to the document is valid in accordance to your field
validations.

```ts
import type { Field } from 'payload'

const emailField: Field = {
  name: 'email',
  type: 'email',
  hooks: {
    beforeChange: [
      ({ value, operation }) => {
        if (operation === 'create') {
          // Perform additional validation or transformation for 'create' operation
        }
        return value
      },
    ],
  },
}
```

In the `emailField`, the `beforeChange` hook checks the `operation` type. If the operation is `create`, it performs
additional validation or transformation on the email field value. This allows for operation-specific logic to be applied
to the field.

### afterChange

The `afterChange` hook is executed after a field's value has been changed and saved in the database. This hook is useful
for post-processing or triggering side effects based on the new value of the field.

```ts
import type { Field } from 'payload'

const membershipStatusField: Field = {
  name: 'membershipStatus',
  type: 'select',
  options: [
    { label: 'Standard', value: 'standard' },
    { label: 'Premium', value: 'premium' },
    { label: 'VIP', value: 'vip' },
  ],
  hooks: {
    afterChange: [
      ({ value, previousValue, req }) => {
        if (value !== previousValue) {
          // Log or perform an action when the membership status changes
          console.log(
            `User ID ${req.user.id} changed their membership status from ${previousValue} to ${value}.`,
          )
          // Here, you can implement actions that could track conversions from one tier to another
        }
      },
    ],
  },
}
```

In this example, the `afterChange` hook is used with a `membershipStatusField`, which allows users to select their
membership level (Standard, Premium, VIP). The hook monitors changes in the membership status. When a change occurs, it
logs the update and can be used to trigger further actions, such as tracking conversion from one tier to another or
notifying them about changes in their membership benefits.

### afterRead

The `afterRead` hook is invoked after a field value is read from the database. This is ideal for formatting or
transforming the field data for output.

```ts
import type { Field } from 'payload'

const dateField: Field = {
  name: 'createdAt',
  type: 'date',
  hooks: {
    afterRead: [
      ({ value }) => {
        // Format date for display
        return new Date(value).toLocaleDateString()
      },
    ],
  },
}
```

Here, the `afterRead` hook for the `dateField` is used to format the date into a more readable format
using `toLocaleDateString()`. This hook modifies the way the date is presented to the user, making it more
user-friendly.

### beforeDuplicate

The `beforeDuplicate` field hook is called on each locale (when using localization), when duplicating a document. It may be used when documents having the
exact same properties may cause issue. This gives you a way to avoid duplicate names on `unique`, `required` fields or when external systems expect non-repeating values on documents.

This hook gets called before the `beforeValidate` and `beforeChange` hooks are called.

By Default, unique and required text fields Payload will append "- Copy" to the original document value. The default is not added if your field has its own, you must return non-unique values from your beforeDuplicate hook to avoid errors or enable the `disableDuplicate` option on the collection.
Here is an example of a number field with a hook that increments the number to avoid unique constraint errors when duplicating a document:

```ts
import type { Field } from 'payload'

const numberField: Field = {
  name: 'number',
  type: 'number',
  hooks: {
    // increment existing value by 1
    beforeDuplicate: [({ value }) => {
      return (value ?? 0) + 1
    }],
  }
}
```

## TypeScript

Payload exports a type for field hooks which can be accessed and used as follows:

```ts
import type { FieldHook } from 'payload'

// Field hook type is a generic that takes three arguments:
// 1: The document type
// 2: The value type
// 3: The sibling data type

type ExampleFieldHook = FieldHook<ExampleDocumentType, string, SiblingDataType>

const exampleFieldHook: ExampleFieldHook = (args) => {
  const {
    value, // Typed as `string` as shown above
    data, // Typed as a Partial of your ExampleDocumentType
    siblingData, // Typed as a Partial of SiblingDataType
    originalDoc, // Typed as ExampleDocumentType
    operation,
    req,
  } = args

  // Do something here...

  return value // should return a string as typed above, undefined, or null
}
```
