Generate TypeScript types from JSON

Paste a sample response and get interfaces you can drop into a project. Nested objects get their own named types rather than being inlined, and an array of objects is merged into one shape with keys missing from some elements marked optional. The inference rules are printed on the page, because guessing why a property came out optional is worse than being told.

This tool runs entirely on your device. Nothing you type here is uploaded, logged or stored.

Settings

Root type name

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Result

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How types are inferred: null becomes null; a key missing from some elements of an array becomes optional; an empty array becomes unknown[]; an array of mixed types becomes a union.

This tool runs entirely in your browser, so the controls above need JavaScript to do anything. The description stays readable either way — nothing here was ever going to be processed on a server.