> ## Documentation Index
> Fetch the complete documentation index at: https://terminal49-vorflux-dev-12120-supported-document-types.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Update a custom field definition

> Update a custom field definition in the Terminal49 API, including its display label, data type constraints, and enum option set for shipments or containers.

Update an existing custom field definition.

## Path parameters

| Parameter | Description                                          |
| --------- | ---------------------------------------------------- |
| `id`      | The unique identifier of the custom field definition |

## Request body

Provide the fields you want to update, such as `display_name`, `description`, `validation`, or `default_format`.

## Notes

You cannot change `api_slug`, `entity_type`, or `data_type` after creation.