Interfaces

Define GraphQL interfaces for type contracts with fields, inheritance, and directive support.

February 4, 2026

GraphQL interfaces define contracts that object types must implement. Interfaces specify a set of fields that implementing types must include, enabling polymorphic queries and consistent field access across related types.

Interface Properties

Property	Required	Description
id	Yes	Unique identifier
name	Yes	Interface name (e.g., "Node", "Connection")
description	No	Explanation of the interface's purpose
fields	Yes	Array of required fields
implementsInterfaces	No	Interfaces this interface extends
directives	No	Directives applied to the interface

Common Interface Patterns

Interface Fields

Fields on interfaces define the contract that implementing types must satisfy:

Property	Required	Description
id	Yes	Unique field identifier
name	Yes	Field name
typeName	No	Direct type name (e.g., "String", "[ID!]")
typeRef	No	Reference to schema definition
nullable	No	Whether the field can return null
isList	No	Whether the field returns an array
listItemNullable	No	Whether list items can be null
description	No	Field explanation
arguments	No	Field arguments (for resolver fields)
directives	No	Directives on this field

{
  "id": "interface-searchable",
  "name": "Searchable",
  "description": "Types that support full-text search",
  "fields": [
    {
      "id": "field-search-content",
      "name": "searchContent",
      "typeName": "String",
      "nullable": false,
      "description": "Concatenated searchable text content"
    },
    {
      "id": "field-search-highlights",
      "name": "searchHighlights",
      "typeName": "[String!]",
      "nullable": true,
      "description": "Highlighted search matches",
      "arguments": [
        {
          "id": "arg-query",
          "name": "query",
          "typeName": "String",
          "nullable": false,
          "description": "Search query to highlight"
        }
      ]
    }
  ]
}

Interface Inheritance

Interfaces can extend other interfaces using the implementsInterfaces property:

{
  "id": "interface-content",
  "name": "Content",
  "description": "Base interface for all content types",
  "implementsInterfaces": ["Node", "Timestamped"],
  "fields": [
    {
      "id": "field-content-title",
      "name": "title",
      "typeName": "String",
      "nullable": false
    },
    {
      "id": "field-content-slug",
      "name": "slug",
      "typeName": "String",
      "nullable": false
    }
  ]
}

The Content interface requires implementing types to include:

Fields from Node: id
Fields from Timestamped: createdAt, updatedAt
Its own fields: title, slug

Directives on Interfaces

Apply directives to interfaces and their fields:

{
  "id": "interface-legacy-entity",
  "name": "LegacyEntity",
  "description": "Interface for legacy system entities being migrated",
  "directives": [
    {
      "directiveId": "deprecated",
      "arguments": {
        "reason": "Use ModernEntity interface instead. Will be removed in v3.0."
      }
    }
  ],
  "fields": [
    {
      "id": "field-legacy-code",
      "name": "legacyCode",
      "typeName": "String",
      "nullable": false,
      "directives": [
        {
          "directiveId": "deprecated",
          "arguments": {
            "reason": "Use 'id' field instead"
          }
        }
      ]
    }
  ]
}

Editor Interface

The Interfaces editor provides:

Interface List - Add, edit, and remove interfaces
Field Management - Add fields with type configuration
Implements Selector - Choose interfaces to extend (excludes self)
Directives Panel - Apply directives to interfaces and fields

Complete Interface Example

{
  "id": "interface-article",
  "name": "Article",
  "description": "Interface for article-type content including blog posts, news items, and documentation pages.",
  "implementsInterfaces": ["Node", "Content", "Publishable"],
  "fields": [
    {
      "id": "field-article-body",
      "name": "body",
      "typeName": "String",
      "nullable": false,
      "description": "Article body content in HTML or Markdown"
    },
    {
      "id": "field-article-excerpt",
      "name": "excerpt",
      "typeName": "String",
      "nullable": true,
      "description": "Short summary for previews and SEO",
      "arguments": [
        {
          "id": "arg-max-length",
          "name": "maxLength",
          "typeName": "Int",
          "nullable": true,
          "defaultValue": "200",
          "description": "Maximum excerpt length"
        }
      ]
    },
    {
      "id": "field-article-author",
      "name": "author",
      "typeName": "User",
      "nullable": false,
      "description": "Article author"
    },
    {
      "id": "field-article-tags",
      "name": "tags",
      "typeName": "String",
      "isList": true,
      "listItemNullable": false,
      "nullable": false,
      "description": "Categorisation tags"
    }
  ],
  "directives": [
    {
      "directiveId": "cacheControl",
      "arguments": {
        "maxAge": 3600
      }
    }
  ]
}