JSON to GraphQL Schema Generator

Paste a JSON object or array into the input and the tool infers a complete GraphQL schema definition. Object keys become field names, and value types are mapped: strings to String, numbers to Int or Float (based on decimal presence), booleans to Boolean, null values to nullable fields, arrays to list types, and nested objects to separate named types. The generator creates a root Query type with a field returning your data type. Array items are analyzed to determine the consistent element type. If an array contains objects, a new named type is created for the element. The output is valid GraphQL SDL ready to use with any GraphQL server implementation.

Both String and ID are built-in GraphQL scalar types that serialize as strings. The difference is semantic intent. String represents arbitrary text content like names, descriptions, and messages. ID represents a unique identifier used to fetch or reference an object, similar to a primary key. ID values should not be assumed to be human-readable. GraphQL clients like Apollo and Relay use the ID type for cache normalization, creating a unique cache key by combining the type name and ID value. The converter infers ID type for fields named id, _id, or ending in Id. All other string values default to the String type. You can manually adjust any field type in the generated schema.

In GraphQL, all fields are nullable by default. A non-null field is marked with an exclamation mark like name: String! meaning it is guaranteed to return a string and never null. The generator analyzes your JSON data to determine nullability. If a field has a null value in any object in the dataset, it remains nullable (no exclamation mark). If a field always has a non-null value across all objects, it is marked as non-null with the ! modifier. For arrays, the list itself and its elements can each be nullable or non-null independently, like [String!]! (non-null list of non-null strings). Conservative nullability is safer since marking a field non-null is a contract your resolvers must fulfill.