JSON to TypeScript Interface Generator

About this tool

Convert a JSON value into TypeScript interfaces, inferred directly from the actual data. Nested objects each become their own named interface, and — unlike a naive converter — array elements that share an identical shape are automatically recognized as the same type and merged into a single interface, rather than generating a needless duplicate for every array. This is inference from a single example, not a JSON Schema, so the result reflects exactly the JSON you paste in.

Key Features

• Infers TypeScript interfaces from real JSON data
• Automatically deduplicates structurally identical object shapes
• Handles nested objects, arrays, and mixed-type arrays
• Quotes property names that aren't valid TypeScript identifiers
• Runs entirely in your browser — your JSON is never uploaded

How to Use

1. Paste your JSON.
2. Optionally set a name for the root interface.
3. Click Generate to see the TypeScript interfaces.

When to use it

• Quickly typing an API response you don't have official types for
• Generating a starting point for types instead of hand-writing them from scratch
• Understanding the actual shape of a deeply nested JSON payload at a glance
• Checking whether two parts of a JSON response actually share the same structure
• Bootstrapping types for a mock or test fixture

Tips & limitations

• This infers types from one example — a field that's sometimes a string and sometimes null in your real data will only show as whichever type appears in the JSON you pasted, not a union of every possibility your API might actually return
• A null value is typed as the literal null — you'll often want to widen this by hand to something like string | null once you know what the field can actually hold
• Property names that aren't valid TypeScript identifiers (starting with a number, containing a hyphen, etc.) are automatically wrapped in quotes, which is valid TypeScript syntax for such keys
• Generated interfaces are ordered innermost-first as they're discovered — TypeScript doesn't require declaration order, so this doesn't affect validity, just reading order

Why identical shapes get merged, not duplicated

The tool computes a structural signature for every object it encounters — its sorted property names and inferred types — and reuses an existing interface whenever two objects share the same signature, rather than naming every occurrence separately.

Frequently Asked Questions

Does this generate a JSON Schema too?

No — this generates TypeScript interfaces directly. If you need a JSON Schema specifically, that's a different output format with its own conventions (validation keywords, $ref, etc.) not covered here.

Why are two structurally identical objects merged into one interface?

Because they represent the same shape — generating a separate, identically-defined interface for each occurrence would just be duplicate code with a different name. This tool detects the match and reuses one interface everywhere that shape appears.

What happens with an array containing objects of different shapes?

Each distinct shape gets its own interface, and the array's type becomes a union of all of them — for example, (TypeA | TypeB)[] — rather than incorrectly forcing every element into one shape.

Can I trust this for a field that's sometimes null and sometimes a value?

Only for the specific example you paste in — if your sample JSON has null for a field that can also hold a string in other API responses, the generated type will only show null. Widen fields like this by hand once you know the full range of values they can hold.

Cite This Tool

Referencing this tool in a paper, article, or bibliography? Copy a ready-made citation below.

NexLove.org. (2026). JSON to TypeScript Interface Generator [Software]. https://nexlove.org/tools/json-to-typescript.html

“JSON to TypeScript Interface Generator.” NexLove.org, 2026, nexlove.org/tools/json-to-typescript.html.

NexLove.org (2026) JSON to TypeScript Interface Generator. Available at: https://nexlove.org/tools/json-to-typescript.html (Accessed: 2026).

@misc{nexlove_json_to_typescript,
  title = {JSON to TypeScript Interface Generator},
  author = {{NexLove.org}},
  year = {2026},
  url = {https://nexlove.org/tools/json-to-typescript.html}
}

Embed This Tool

Add the live JSON to TypeScript Interface Generator tool to your own website with this snippet — it loads the real, working tool in an iframe, not a static screenshot.

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