Specific GraphQL-related Content-Type header value `application/graphql` was added last year: https://github.com/graphql-java-kickstart/graphql-java-servlet/issues/71 However, it seems this hasn't been added in the Usage chapter of the README file, leading probably to people to ignore this: https://github.com/graphql-java-kickstart/graphql-java-servlet#usage