> ## Documentation Index
> Fetch the complete documentation index at: https://docs.automatebusiness.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Update Custom Field Value

To update a custom field for a contact, use the [Update Contact](/automate-chats/api-reference/contacts/update-contact) (`PUT /api/contacts/{id}`) endpoint.

Provide the `customFields` array containing the `fieldId` and the new `value`. If a custom field is not included in the payload, its current value will be retained.

**Example Payload:**

```json theme={null}
{
  "customFields": [
    {
      "fieldId": "your_custom_field_id",
      "value": "New Updated Value"
    }
  ]
}
```