JSON to TypeScript Interfaces

Generate TypeScript interfaces from JSON

Hand-writing TypeScript interfaces for API responses is tedious and error-prone. You paste a sample response into your editor, then transcribe every field name and guess at the type, hoping you do not miss any optional fields. Lintify automates that: paste a sample JSON document, and the generator walks the structure recursively to produce a TypeScript interface per object shape, with the right types for primitives, arrays, and nested objects.

If you paste a JSON array of objects, the generator merges the keys of every object in the array. Any key that is missing from at least one element is marked optional (with a ?). This is more accurate than picking one element as the source of truth, because real API responses often have nullable or omitted fields.

Union types for mixed samples

If a field has different types across samples — a string in one object and a number in another — the generator emits a union type (string | number). This is more useful than picking one type and silently breaking on the other input. The TypeScript compiler will force you to handle both cases, which is what you want for data you do not control.

String literal unions instead of enums

Lintify emits string literal unions (type Status = 'active' | 'inactive') rather than TypeScript enums. This matches the modern recommendation — literal unions are lighter at runtime (no generated object), work better with type narrowing, and are easier to refactor. If you need a real enum for runtime reflection, the conversion is trivial in your editor.

Interface naming

The top-level interface is namedRootObject by default. Nested objects get names derived from their parent key — for example,users[0].address becomes an interface namedAddress. You can rename them after generation to match your codebase conventions. The names are unique within the generated file, so collisions are resolved by appending a numeric suffix.