What is JSON to Effect Schema Generator?

Effect Schema (@effect/schema) is a runtime validation and type inference library for TypeScript, part of the Effect ecosystem. It uses Schema.Struct to define object schemas and provides automatic TypeScript type extraction via Schema.Schema.Type. This tool converts your JSON data into Effect Schema definitions automatically, handling nested objects, arrays, optional fields, and type alias exports.

How to Use

Set the root schema name in the options bar
Toggle "Wrap with Schema.optional()" to wrap all fields with Schema.optional() for optional field support
Toggle "Export type aliases" to generate type exports using Schema.Schema.Type
Paste your JSON data into the input area
Click "Generate Effect Schema" to create the schema
Copy the output and use it directly in your TypeScript project

Why Use This Tool?

Automatically infer Effect Schema types from JSON values

Nested objects get separate exported Schema.Struct definitions for reusability

Optional field detection wraps fields with Schema.optional()

Type alias exports via Schema.Schema.Type<typeof Schema> for full type safety

Children-first ordering ensures nested schemas are defined before the root

Null values map to Schema.Null for explicit null handling

Tips & Best Practices

Use realistic sample data — type inference depends on actual values
For nullable fields, manually change to Schema.Union(Schema.String, Schema.Null)
Add refinements with Schema.pipe() for constraints like Schema.String.pipe(Schema.minLength(1))
Effect Schema integrates seamlessly with the Effect runtime for composable error handling
Use Schema.decodeUnknownSync(Schema)(data) for runtime validation

Frequently Asked Questions

What is Effect Schema?

Effect Schema (@effect/schema) is a TypeScript runtime validation and type inference library that is part of the Effect ecosystem. It provides Schema.Struct for defining object schemas, automatic TypeScript type extraction via Schema.Schema.Type, and composable validation with the Effect runtime. It is designed for high-performance, tree-shakeable schema definitions.

How does JSON map to Effect Schema types?

JSON strings map to Schema.String, numbers to Schema.Number, booleans to Schema.Boolean, null to Schema.Null, arrays to Schema.Array(Schema.Type), and objects to Schema.Struct({...}). Optional fields can be wrapped with Schema.optional(). Nested objects are extracted as separate Schema.Struct definitions with their own type aliases.

What is Schema.optional() used for?

Schema.optional() wraps a schema to indicate that the field may be omitted from the data. This is different from nullable fields (which use Schema.Union with Schema.Null). When you enable the "Wrap with Schema.optional()" option, all fields in the generated schema will be wrapped with Schema.optional(), making every field optional in the type definition.

How do I validate data with Effect Schema?

Use Schema.decodeUnknownSync(MySchema)(data) for synchronous validation, or Schema.decodeUnknown(MySchema)(data) for Effect-based async validation. For safe parsing without throwing, use Schema.decodeUnknownOption or Schema.decodeUnknownEither. These return Option or Either types respectively, allowing composable error handling.

Is my data sent to a server?

No, all processing happens entirely in your browser. Your JSON data never leaves your device.

JSON to Effect Schema Generator