TypeScript Type from JSON

Frequently Asked Questions

How is this different from quicktype?

Quicktype is deterministic and great for large schemas. This tool is LLM-backed, so it picks better interface names from context, handles discriminated unions more intelligently, and writes cleaner output for small-to-medium JSON. For giant schemas, quicktype is still your friend.

Does it handle arrays with mixed types?

Yes. When items in an array differ, the tool generates a union type like <code>(User | Admin)[]</code>. When items share a shape but some fields are optional, it produces a single interface with the optional fields marked with <code>?</code>.

Can I paste the output directly into my codebase?

Yes. The output is valid TypeScript syntax — interfaces plus nested sub-interfaces, properly exported. Drop it into a <code>.ts</code> or <code>.d.ts</code> file. If you use <code>type</code> aliases instead of <code>interface</code>, a quick find-replace converts them.

What about nullable fields?

The tool treats <code>null</code> as an explicit union (<code>string | null</code>) when the value can legitimately be null at runtime. For fields that are sometimes missing from the JSON, it uses the <code>?</code> optional marker. Both patterns are common in real API responses.