204-no-content-type

Disallows a Content-Type response header on status 204.

Attribute	Value
Category	Operations
Maturity	Gold
OpenAPI	Swagger 2.0; OpenAPI 3.0, 3.1, 3.2
Starter	Off
Lenient–Complete	Error

Intent

204 No Content has no response body, so declaring its media type is misleading.

Flags

A response whose status is exactly 204 and whose headers include Content-Type, matched case-insensitively.

Does not flag

Other status codes or 204 responses without that header. Body declarations are handled by response-body-not-allowed.

See it fail

responses:
  '204':
    description: Deleted
    headers:
      Content-Type:
        schema:
          type: string

Diagnostic: 204 responses should not define `Content-Type` header.

Fix it

responses:
  '204':
    description: Deleted

Configure

profiles:
  default:
    rules:
      extends: [recommended]
      override:
        204-no-content-type: warn

Nearby: response-body-not-allowed, content-type-header-declared.