GraphQL Schema Definition Language (SDL) is the syntax used to define the structure of a GraphQL API — including types, fields, and their relationships. It is the standard way to describe a GraphQL schema.

How does the type inference work?

The tool inspects each JSON value: numbers without decimals become Int, numbers with decimals become Float, true/false become Boolean, and strings become String. Fields named 'id', '_id', or 'uuid' are inferred as ID. Arrays produce list types (e.g. [String]), and nested objects generate separate named types.

Are nullable fields handled correctly?

Yes. In the generated schema, all fields are nullable by default (which is idiomatic GraphQL). You can add exclamation marks (!) to mark fields as non-null after generation if needed.

Does this tool send my data to a server?

No. The entire conversion runs in your browser using JavaScript. Your JSON data never leaves your device — there is no backend, no API call, and no data collection.

Can I convert nested JSON objects?

Yes. Nested objects are converted to separate named GraphQL types and referenced by name in the parent type. Arrays of objects produce list types referencing the generated nested type.

What if my JSON has mixed-type arrays?

The tool inspects the first element of each array to determine its type. For mixed-type arrays, it falls back to String. It is recommended to review and adjust the generated schema for edge cases.

Free GraphQL Schema Generator

Convert JSON to
GraphQL Schema

Paste any JSON object and instantly get a complete GraphQL SDL with smart type inference, nested types, and list fields. No login. No server. Just paste and copy.

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Smart Type Inference

Automatically detects String, Int, Float, Boolean, and ID types from JSON values.

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Nested & List Types

Handles deeply nested objects and arrays, generating correct GraphQL types recursively.

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Instant & Private

Runs entirely in the browser — nothing is uploaded to any server. Fast, private, and free.

JSON → GraphQL Schema

JSON Input

GraphQL Schema (SDL)

type Root {
  id: ID
  name: String
  email: String
  age: Int
  score: Float
  isActive: Boolean
  address: Address
  tags: [String]
  posts: [Post]
}

type Address {
  street: String
  city: String
  zip: String
}

type Post {
  id: ID
  title: String
  published: Boolean
  likes: Int
}

All conversion runs in your browser — your data never leaves your device.

Frequently Asked Questions

Everything you need to know about JSON to GraphQL.