GraphQL Schema Validator v2

This validator performs semantic checks beyond syntax: it verifies that every referenced type actually exists in the schema, that types implementing interfaces declare all required fields, that union members are valid object types, and that no unknown directives are used. It also generates an introspection preview listing every type with its field count — the same data a GraphQL server exposes via the __schema query.

In GraphQL, if a type declares it implements an interface (e.g., type Dog implements Animal), it must define every field that the interface requires, with matching or compatible types. This validator parses all interface definitions, collects their required fields, then checks each implementing type to confirm those fields are present. Missing fields produce errors.

A GraphQL union can only contain concrete object types — not scalars, not interfaces, not input types, not enums. For example, union SearchResult = User | Post | Article is valid. union SearchResult = String | User is not. This validator reads each union's member list and confirms every member resolves to a defined object type in the schema.

The GraphQL spec defines four built-in directives: @deprecated (marks fields, enum values, arguments as deprecated), @skip and @include (conditional execution in queries), and @specifiedBy (for custom scalars with a URL spec). Any directive not in this list — such as @auth, @cacheControl, or custom directives — will be flagged as unknown unless your schema explicitly defines them with a directive definition.

GraphQL servers expose a built-in __schema query that returns all types, fields, and directives in the schema. This tool simulates that output by parsing your SDL and listing every type by kind (type, interface, enum, input, union, scalar) along with its field count. It is useful for auditing how large your schema is and for verifying that all expected types parsed correctly.

No. All parsing and validation runs entirely in your browser using JavaScript. Your GraphQL schema — which may describe your data model, access control structure, and API surface — never leaves your machine. No network requests are made when you click Validate.