How does it handle nested objects?

Nested objects are extracted into separate named interfaces based on the property key. For example, a "address" property with an object value generates an Address interface.

What about arrays of objects?

All objects in an array are merged to create a single interface that covers all possible keys. This handles APIs that return slightly different shapes per item.

Can I customize the interface name?

Yes. Change the root name field to set the top-level interface name. Nested interfaces are automatically named based on their property keys in PascalCase.

JSON to TypeScript

Code Converters

Generate TypeScript interfaces from JSON data

By DevToolHQ teamUpdated 2026-04-15100% client-sideMethodology

100% client-side processing

JSON Input

Root name:

About JSON to TypeScript

Generates TypeScript interface definitions from JSON data. Paste any API response, database row, or configuration object and get typed interfaces you can drop directly into your TypeScript project. This eliminates the manual work of writing types by hand when integrating with external APIs or migrating JavaScript code to TypeScript. The generator handles nested objects by creating separate named interfaces for each nested level, using the property key as the basis for the interface name in PascalCase. Arrays of primitives become typed as number[] or string[]. Arrays of objects are analyzed by merging all object shapes in the array — so if some items have optional fields that others omit, those fields appear as optional (field?: type) in the generated interface. Null values produce field?: type | null. For real-world API responses where a field might be a string in one response and null in another, sampling multiple responses and pasting the full array gives more accurate optional type coverage than a single sample. The root interface name is configurable — change "Root" to whatever domain entity the JSON represents. The output is ready to copy into a .ts or .d.ts file immediately, and works as a starting point even if the API schema has edge cases you need to refine manually.