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JSON to TypeScript

Turn one or more JSON samples into merged TypeScript interfaces or type aliases, entirely in your browser.

Types are inferred from your sample data, not from an API contract: a field that is always null in the sample is typed as null, and a field that is always a number is typed as number even if the real API sometimes sends a string. Widen those declarations yourself before using them in production. Blank-line-separated documents and top-level arrays are merged into one union: a key missing from some samples becomes optional, and disagreeing types become unions like string | number | null.

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What Is JSON to TypeScript?

The JSON to TypeScript generator infers declarations from data instead of guessing from a single object. Feed it several samples, or an array of them, and it merges the shapes: a key missing from one item becomes optional, a key that is sometimes a string and sometimes a number becomes a union, and anything null in every sample stays null so you can widen it deliberately. Nested objects get their own named interfaces, keys that are not valid identifiers are quoted, and names that would collide are disambiguated rather than overwritten.

Who Uses the JSON to TypeScript?

Frontend developers writing against an API response, and anyone documenting a payload for a team, get a working starting point in seconds instead of an hour of typing.

How to Use the JSON to TypeScript

  1. Paste one JSON document or several separated by blank lines.
  2. Set the root name and choose interface or type, export prefix and all-optional output.
  3. Copy the declarations or download types.ts, then correct fields the sample could not prove.

Why Choose Our JSON to TypeScript?

  • Merging across samples produces optional markers and unions rather than one lucky guess
  • Named interfaces for nested shapes with collision-safe naming
  • The emitted text is structurally checked before it is shown to you

Try the JSON to TypeScript above — it is free, fast, and works on any device. Bookmark this page to return whenever you need it.