GraphQL Schema Validator Online — SDL Check

Validate GraphQL schema SDL locally with buildSchema. Spec-accurate errors — not a query runner. Format with Beautify GraphQL.

Loading…
Validate GraphQL documentation
Validate GraphQL schema SDL with buildSchema.

Developer notes

Uses graphql buildSchema only (dynamic import) — schema SDL, not query execution. GraphQL.js typically requires a Query root type unless the schema defines otherwise. Syntax errors include line/column when available; some semantic errors may omit locations. Formatting stays on Beautify GraphQL (Prettier) — there is no format-graphql slug. Max input 512 KiB. The results panel shows Valid/Invalid with line/column issues and a copy-error action.

Use cases

Catch undefined types and SDL syntax errors before deploy. Paste a schema document for a quick local check. Pair with Beautify GraphQL for formatting.

Examples

Valid SDL with Query

Before

type Query { hello: String pet(id: ID!): Pet } type Pet { id: ID! name: String! }

After

Status: valid

Undefined type

Before

type Query { hello: Foo }

After

Unknown type "Foo"

Validate GraphQL FAQ

Common questions

Does this validate queries?

No — only schema SDL via buildSchema. It does not execute queries or introspect a live server.

Do I need a Query type?

Yes in typical GraphQL.js defaults: a Query root is required unless your schema definition says otherwise. Missing Query usually fails validation.

Where do I format GraphQL?

Use Beautify GraphQL (Prettier). There is no separate format-graphql tool on FastMinify.

Related tools?

Format with Beautify GraphQL. For JSON Schema / OpenAPI, browse the API tools hub.

API & schemas

OpenAPI tools to format, validate, and lint your specs.

Explore other tool categories