---
title: "GraphQL | Non-Nullable Fields"
description: "<p>In GraphQL, fields can be marked as mandatory (non-nullable), meaning they must always return a value. If a non-nullable field is queried and the API cannot provide data, it will return an error. This prevents unexpected null values in responses and ensures data integrity.</p><p>To enable strict type checks for non-nullable fields include the following header in your GraphQL API request:</p><pre>x-graphql-strict-type-checks: true</pre><p class=\"note\"><strong>Note</strong>: Reach out to our <a href=\"mailto:support@contentstack.com\" target=\"_blank\">support</a> team to enable this feature for your organization.</p><p>When non-nullability is enabled, the GraphQL schema will reflect the strict type enforcement. Below is a comparison of how field types change:</p><div classname=\"cs-table-wrapper\"><div classname=\"cs-table\"><table><thead><tr><td><strong>Field Type</strong></td><td><strong>GraphQL (Nullable)</strong></td><td><strong>GraphQL (Non-Nullable)</strong></td></tr></thead><tbody><tr><td>Text</td><td><p><span class=\"code\">String</span></p></td><td><p><span class=\"code\">String!</span></p></td></tr><tr><td>Number</td><td><p><span class=\"code\">Int</span></p></td><td><p><span class=\"code\">Int!</span></p></td></tr><tr><td>Date</td><td><p><span class=\"code\">ISODate</span></p></td><td><p><span class=\"code\">ISODate!</span></p></td></tr><tr><td>Link</td><td><p><span class=\"code\">Link</span></p></td><td><p><span class=\"code\">Link!</span></p></td></tr><tr><td>Reference</td><td><p><span class=\"code\">[CTReferenceEdge]</span></p></td><td><p><span class=\"code\">[CTReferenceEdge!]!</span></p></td></tr><tr><td>System</td><td><p><span class=\"code\">EntrySystemField</span></p></td><td><p><span class=\"code\">EntrySystemField!</span></p></td></tr></tbody></table></div></div><p>Enabling non-nullable fields ensures more predictable API responses and prevents missing mandatory field data in queries.</p>"
url: "https://www.contentstack.com/docs/developers/apis/graphql-content-delivery-api/non-nullable-fields"
product: "Contentstack"
doc_type: "guide"
audience:
  - developers
  - admins
version: "current"
last_updated: "2026-06-02"
---

# GraphQL | Non-Nullable Fields

In GraphQL, fields can be marked as mandatory (non-nullable), meaning they must always return a value. If a non-nullable field is queried and the API cannot provide data, it will return an error. This prevents unexpected null values in responses and ensures data integrity.

To enable strict type checks for non-nullable fields include the following header in your GraphQL API request:

```
x-graphql-strict-type-checks: true
```

**Note**: Reach out to our [support](mailto:support@contentstack.com) team to enable this feature for your organization.

When non-nullability is enabled, the GraphQL schema will reflect the strict type enforcement. Below is a comparison of how field types change:

**Field Type**

**GraphQL (Nullable)**

**GraphQL (Non-Nullable)**

Text

String

String!

Number

Int

Int!

Date

ISODate

ISODate!

Link

Link

Link!

Reference

\[CTReferenceEdge\]

\[CTReferenceEdge!\]!

System

EntrySystemField

EntrySystemField!

Enabling non-nullable fields ensures more predictable API responses and prevents missing mandatory field data in queries.