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JSON to Type Generator Tool - Multi-Language Type Definition Generator with Smart Inference

First Published: 2026-04-02
Last Updated: 2026-04-02

This tool generates typed definitions from JSON data for multiple programming languages. Paste your JSON (or multiple samples separated by ---) and instantly generate TypeScript interfaces, TypeScript type aliases, Zod schemas, Go structs, Rust structs, Python dataclasses, or Java classes. Smart inference detects ISO 8601 dates and UUIDs, and multi-sample mode automatically identifies optional properties.

Features

• 7 Output Languages — TypeScript interface, TypeScript type alias, Zod schema (runtime validation), Go struct (with aligned json tags), Rust struct (serde-compatible), Python dataclass, Java class (Jackson-annotated)
• Multi-Sample Merging — Paste multiple JSON objects separated by --- to automatically detect optional properties and union types from differences across samples
• Smart Type Detection — Automatically recognizes ISO 8601 date strings and UUID patterns, annotating them with JSDoc comments in TypeScript output and using datetime/uuid validators in Zod
• Nested Type Extraction — Optionally extract nested objects into separate named types or keep them inline
• Configurable Output — Customize root type name, indentation style, export keyword, readonly modifier, and smart detection toggles
• Null Safety — Properly handles null values as union types (e.g., string | null, .nullable() in Zod, Option<T> in Rust)
• Idiomatic Code Generation — Each language output follows its conventions: PascalCase for Go fields, snake_case for Rust/Python, camelCase for Java, serde rename attributes, Jackson annotations, column-aligned Go struct tags
• File Upload — Drag and drop or browse to upload JSON files (up to 5 MB)
• Complete Client-Side Processing — All processing happens in your browser. No data is ever transmitted to any server.

How to Use

1. Paste your JSON data into the input area, or drag and drop a JSON file.
2. For multi-sample merging, paste multiple JSON objects separated by --- on its own line. Properties that appear in some but not all samples will be marked as optional.
3. Select the output language from the dropdown (TypeScript Interface, Type Alias, Zod, Go, Rust, Python, or Java).
4. Configure options: root type name, indentation, export/readonly modifiers, date/UUID detection, and nested type separation.
5. Click Generate to produce type definitions.
6. Click Copy Result to copy the generated code to your clipboard.

Important Notes

• Generated types are based on the structure and values of the provided JSON. Always review the output for correctness before using in production.
• Array types are inferred from the union of all element types. Empty arrays produce unknown[] (TypeScript) or equivalent.
• Multi-sample mode works best with objects of the same shape. Samples with different root types (e.g., one array and one object) will produce a union type.
• Smart date detection matches ISO 8601 patterns (e.g., 2024-01-15, 2024-01-15T10:30:00Z). Strings that happen to match but are not dates may be incorrectly classified; toggle the option off if needed.
• Go struct output includes time.Time for detected dates; ensure you import the time package.
• Zod output includes import { z } from 'zod'; ensure the Zod library is installed in your project.