---
title: MetafieldDefinition - Shop Users API
description: |-
  A MetafieldDefinition is a Permissible type. It is managed by a Client and defines the shape of the
  data stored in in a Metafield. Control and access of a MetafieldDefinition is determined by AccessGrants
  that link the definition to Clients or Namespaces.
api_version: unstable latest
source_url:
  html: https://shopify.dev/docs/api/shop-users/latest/objects/MetafieldDefinition
  md: https://shopify.dev/docs/api/shop-users/latest/objects/MetafieldDefinition.md
---

# Metafield​Definition

object

A MetafieldDefinition is a Permissible type. It is managed by a Client and defines the shape of the data stored in in a Metafield. Control and access of a MetafieldDefinition is determined by AccessGrants that link the definition to Clients or Namespaces.

## Fields

* access

  [Custom​Data​Access​Type](https://shopify.dev/docs/api/shop-users/latest/objects/CustomDataAccessType)

  List of the active policies associated with this Definition. Policies represent ownership of the Definition and can be granted to Clients and Nampespaces.

* description

  [String](https://shopify.dev/docs/api/shop-users/latest/scalars/String)

  Developer facing description.

* key

  [String!](https://shopify.dev/docs/api/shop-users/latest/scalars/String)

  non-null

  Developer facing identifier for the resource.

* name

  [String](https://shopify.dev/docs/api/shop-users/latest/scalars/String)

  Developer facing display name.

* namespace

  [String](https://shopify.dev/docs/api/shop-users/latest/scalars/String)

  Developer facing path to identifier for the resource.

* type

  [Metafield​Definition​Type!](https://shopify.dev/docs/api/shop-users/latest/objects/MetafieldDefinitionType)

  non-null

  One of the types available in the Metafield developer documentation (<https://shopify.dev/docs/apps/custom-data/metafields/types>), except JSON.

* uuid

  [ID!](https://shopify.dev/docs/api/shop-users/latest/scalars/ID)

  non-null

  Internal identifier for the resource.

* validations

  [\[Custom​Data​Metafield​Definition​Validation​Type!\]](https://shopify.dev/docs/api/shop-users/latest/objects/CustomDataMetafieldDefinitionValidationType)

  A list of validation options for the metafields that belong to the metafield definition.

***

## Map

### Fields with this object

* [Metafield.definition](https://shopify.dev/docs/api/shop-users/latest/objects/Metafield#field-Metafield.fields.definition)

***

## Interfaces

* [Custom​Data​Permissible](https://shopify.dev/docs/api/shop-users/latest/interfaces/CustomDataPermissible)

  interface

***

## MetafieldDefinition Implements

### Implements

* [Custom​Data​Permissible](https://shopify.dev/docs/api/shop-users/latest/interfaces/CustomDataPermissible)