GraphQL Schema Validator Online — SDL Check
Validate GraphQL schema SDL locally with buildSchema. Spec-accurate errors — not a query runner. Format with Beautify GraphQL.
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
After
Undefined type
Before
After
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.
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