JSON Multi-Converter: 7-in-1 Code & Schema Generator
One JSON in, seven outputs: TypeScript interfaces, Zod schemas, Mongoose models, SQL DDL, JSON Schema, OpenAPI and mock data. Free and fully client-side.
Select a tab and paste JSON to beginโฆ
The JSON multi-converter generates seven outputs from a single payload: TypeScript interfaces, Zod schemas, Mongoose models, SQL DDL, JSON Schema Draft-07, OpenAPI components and mock fixtures. Paste JSON on the left, pick a target format, and the generated code appears on the right.
The multi-converter runs one JSON payload through seven generators without making you visit seven pages: TypeScript interfaces, Zod schemas, Mongoose models, SQL DDL, JSON Schema Draft-07, OpenAPI components, and mock fixtures. All of it is generated in the browser, so an API response containing real customer data can be turned into types without being uploaded anywhere.
Which output should I use for what?
They answer different questions. TypeScript gives you compile-time safety and editor autocomplete but disappears at runtime. Zod checks the data at the boundary and derives the TypeScript type from the same declaration, so it is the better default for anything crossing a network. JSON Schema is the portable, language-neutral contract to publish or share. OpenAPI is that contract embedded in API documentation. Mongoose and SQL are persistence models. Mock data closes the loop for tests.
How good is inference from a single sample?
It is a strong first draft and a weak final answer, because one sample cannot show you what varies. A field that is null in your example has an unknowable type. A field absent from your example will be absent from the output. An array that happens to hold one element looks homogeneous even when the real data is a union. And a numeric string looks like a string even when the API sometimes sends a number. Paste the messiest realistic record you can find, then widen the generated types by hand where you know the API is looser.
Why generate rather than hand-write?
Because transcription is where the bugs live. Hand-typing a forty-key response into an interface reliably produces a typo, a wrong optional marker, or a field silently typed any โ and the compiler cannot catch a type that merely disagrees with reality. Generating from the actual payload makes the types match the data by construction. Treat the output as a starting point you review, not as something to commit unread.
How to use the JSON Multi-Converter
Takes under a minute. Nothing is uploaded โ every step runs in this browser tab.
- Paste one JSON payload
Put a representative object or API response into the left-hand input pane. Use a record with all optional fields populated so inference has the most to work with.
- Choose a target
Switch between TypeScript, Zod, Mongoose, SQL, JSON Schema, OpenAPI, and mock data. The input stays put, so you can compare outputs without re-pasting.
- Read the generated code
The right-hand pane updates as you switch targets, showing the generated artefact for the current selection.
- Copy what you need
Copy each output in turn โ a typical use is taking the TypeScript interface and the Zod schema together.
When to use it
- Bootstrapping a typed API client from a single sample response
- Producing types and a runtime validator for the same payload in one sitting
- Drafting an OpenAPI component schema from an endpoint that has no documentation
- Comparing how the same data models as a JSON Schema, a Zod schema, and SQL DDL
- Generating mock fixtures shaped exactly like the real response for tests
Step-by-step guides for this tool
Task-specific walkthroughs covering the most common ways this tool gets used.
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Frequently Asked Questions
What is the JSON Multi-Converter?
An all-in-one developer workspace that converts a single JSON payload into 7 different targets simultaneously: TypeScript types, Zod schemas, Mongoose models, SQL DDL, JSON Schema Draft-07, OpenAPI schemas, and synthetic mock fixtures.
Do I have to paste my JSON again for each output format?
No. Paste once on the left and switch target tabs on the right โ every format is generated from the same payload, which is the point of a multi-converter over seven separate tools.
Can I rename the generated interfaces, models and tables?
Yes. Each target has its own name field: a root name for the TypeScript and Zod output, a model name for Mongoose, a schema name for OpenAPI, and a table name plus dialect (PostgreSQL, MySQL or SQLite) for the SQL output.
Is the JSON multi-converter free, and does it upload my payload?
It is free with no account, and nothing is uploaded. All seven generators run in your browser, so a production API response with real identifiers stays on your machine.
Related Developer Tools
- Standards & references:
- JSON
- TypeScript
- Zod
- JSON Schema
- OpenAPI Specification
Last reviewed by the JSON2X Engineering Team.