JSON to Swift Codable Generator

Generate Swift structs conforming to Codable from a JSON sample, with camelCase properties, CodingKeys for renamed keys and optionals for missing values.

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Input

Generate Swift types from JSON

JSON sampleRoot type name

Output

Swift

488 characters

import Foundation

struct Order: Codable {
    let id: Int
    let total: Double
    let items: Int?
    let coupon: String?
}

struct Profile: Codable {
    let name: String
    let avatarUrl: String?

    enum CodingKeys: String, CodingKey {
        case name
        case avatarUrl = "avatar_url"
    }
}

struct User: Codable {
    let id: Int
    let email: String
    let active: Bool
    let score: Double
    let roles: [String]
    let profile: Profile
    let orders: [Order]
}

Structs conform to Codable. A key that is not a camelCase Swift name gets a CodingKeys entry, so JSONDecoder reads it without a global keyDecodingStrategy. Nullable or missing keys are optionals. Types come from this one sample: give fields that are null here a real value to type them.

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About this tool

Method, assumptions, practical next steps, and limits.

CodingKeys or a decoding strategy

JSONDecoder.keyDecodingStrategy = .convertFromSnakeCase converts snake_case keys for every type at once, which saves writing CodingKeys, but it applies to the whole decoder and cannot handle keys that are not snake_case. Explicit CodingKeys, as generated here, work with any decoder settings. Apple's Encoding and Decoding Custom Types article covers both.

Dates and numbers

Timestamps arrive as String here; set decoder.dateDecodingStrategy = .iso8601 and change the property to Date to decode them directly. Whole numbers become Int and fractions Double.

Frequently asked questions

Why does decoding fail with keyNotFound?

A non-optional property's key was missing from the JSON. Make the property optional, or give the struct a custom init(from:) with decodeIfPresent and a default.

Should I use let or var?

let suits values decoded once and passed around. Use var if the app edits the model before encoding it again.

Is what I paste sent anywhere?

No. The tool runs entirely in your browser with JavaScript. Nothing you type or paste is sent to our server or stored.

JSON to Swift Codable Generator

Generate Swift types from JSON

Swift

CodingKeys or a decoding strategy

Dates and numbers

Frequently asked questions

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