Turn a JSON Response Into Types

Typing an API response by hand is slow and easy to get wrong. Paste a real JSON sample and QodeCat writes the TypeScript declarations for you, live as you type, ready to copy into your project.

• Named nested types: Every nested object becomes its own interface, named after its key.
• Optional fields: A key that is missing in some items of an array is marked with ?.
• Unions: Mixed arrays become union types, null values become T | null and empty arrays become unknown[].
• Options: Root name, interface or type alias, readonly properties and the export keyword.

Why use this tool?

Learns From All Array Items

Instead of looking only at the first element, the generator merges every object in an array. Keys that appear only sometimes become optional, and a field that is a string in one item and null in another becomes string | null.

Clear Errors, Private Data

If the JSON is invalid, you see the line and column of the problem. The conversion runs entirely in your browser, so API responses with customer data or tokens are never uploaded.

Frequently Asked Questions