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JSON to TypeScript
Infer useful TypeScript definitions locally
Generate interfaces or type aliases for nested objects, arrays, primitives, nulls and mixed values without uploading the source.
No definitions yet
Inference runs entirely in this browser.
Deterministic inference
Consistent types from representative samples
Objects generate named definitions, arrays infer their element types, mixed values become stable unions, and null remains explicit. Object-array samples are merged so fields missing from some records become optional.
Safe property names
Valid TypeScript identifiers remain unquoted. Names containing spaces, punctuation or other unsafe characters are emitted as quoted properties with a clear warning.
Inference has limits
JSON values cannot reveal every intent
An empty array becomes unknown[], numbers cannot reveal branded or integer types, and optional fields are inferred only when multiple objects appear in the same array sample.
Focused TypeScript output
Choose interfaces or type aliases, copy the result, or download a .ts file. Zod schema generation is intentionally outside this module.
FAQs
JSON-to-TypeScript questions
How are mixed arrays represented?
Distinct inferred element types are combined into a deterministic union. Object samples are merged before joining other value types.
Does generation upload JSON?
No. File reading, parsing, inference and output generation happen locally in your browser.