How does it handle nested objects?

Each nested JSON object becomes its own Swift struct, named after the key it appeared under. If the same key produces two different shapes, the tool appends a number to keep the types distinct.

What happens with null values?

A field that is null becomes an optional Swift property. Since the JSON type is unknown when a value is null, the tool falls back to an optional String and adds a comment so you can adjust it by hand.

Does it support snake_case JSON keys?

Yes. Enable "Generate CodingKeys" and snake_case keys like user_name are converted to camelCase Swift properties (userName), with a CodingKeys enum mapping each property back to its original JSON key.

What if my JSON is an array at the top level?

The tool merges the fields across all elements in the array into a single struct. Keys that are missing from some elements are marked optional.

Does this send my JSON anywhere?

No. Parsing and code generation both run in your browser with JavaScript. Nothing is uploaded to a server.

Are the property types always correct?

Types are inferred from the sample JSON you paste, so an integer field that could hold a decimal elsewhere in your real data may need to be widened to Double by hand. Review the generated code before shipping it.

JSON to Swift

Name: JSON to Swift
Availability: InStock
Author: Nham Vu

Paste JSON and get matching Swift Codable structs, with nested types and optional fields inferred automatically.

JSON Input

Root type name

Use var instead of let Generate CodingKeys for snake_case

Paste JSON on the left and click Generate Swift

Swift Codable structs

Copied!

Summary

Paste JSON and get matching Swift Codable structs, with nested types and optional fields inferred automatically.

How it works

Paste a JSON object or array in the left panel.
Set a root type name and pick your struct options.
The tool parses the JSON and infers a Swift type for every field.
Nested objects and arrays of objects become their own Codable structs.
Copy the generated Swift code with one click.

Use cases

Turn an API response sample into Codable structs for an iOS app.
Scaffold Swift models before writing full networking code.
Check whether a JSON payload maps cleanly to strict Swift types.
Generate CodingKeys for JSON that uses snake_case keys.
Prototype a Swift model from a JSON fixture used in tests.

Frequently Asked Questions

Last updated: 2026-07-23 · Reviewed by Nham Vu