JSON to Swift Codable

JSON → Swift Codable models. CodingKeys are emitted only when a JSON key differs from the Swift property, and reserved words are backtick-escaped.

Emit struct (uncheck for final class)

JSON{
  "id": 42,
  "display_name": "Ada Lovelace",
  "is_verified": true,
  "rating": 4.75,
  "location": {
    "city": "London",
    "postal_code": "NW1 6XE"
  },
  "tags": ["math", "compiler"],
  "devices": [
    { "model": "iPhone 15", "os_version": "17.4" }
  ]
}

Swiftimport Foundation

struct Root: Codable {
    let id: Int
    let displayName: String
    let isVerified: Bool
    let rating: Double
    let location: Location
    let tags: [String]
    let devices: [Device]

    enum CodingKeys: String, CodingKey {
        case id
        case displayName = "display_name"
        case isVerified = "is_verified"
        case rating
        case location
        case tags
        case devices
    }
}

struct Device: Codable {
    let model: String
    let osVersion: String

    enum CodingKeys: String, CodingKey {
        case model
        case osVersion = "os_version"
    }
}

struct Location: Codable {
    let city: String
    let postalCode: String

    enum CodingKeys: String, CodingKey {
        case city
        case postalCode = "postal_code"
    }
}

// Decode with: try JSONDecoder().decode(Root.self, from: data)

JSON to Swift Codable — Free Online Tool

Generates Swift Codable models from a JSON sample as structs or final classes, mapping JSON types to Int, Double, Bool, String and arrays, emitting a CodingKeys enum only when a wire key differs from the lowerCamelCase property, backtick-escaping Swift reserved words, and reusing one model for repeated object shapes.

How to use the JSON to Swift Codable

Open the tool above — it runs entirely in your browser, so your input never leaves this page.
Paste or type your input into the field, then press the relevant button (e.g. Encode / Decode, Generate, or Convert).
Copy the result from the output area with the copy button orCtrl/Cmd + C.
No signup, no upload, and no tracking — repeat as often as you need.

Frequently asked questions

Why is there no CodingKeys enum on some structs?

It is emitted only when at least one JSON key differs from the Swift property name. When every key already matches the lowerCamelCase property, Swift's synthesized Codable conformance is enough and the extra enum would be noise.

Should I pick struct or final class?

Struct is the Swift default for data models — value semantics, no reference cycles, cheaper to copy. Choose final class when you need reference identity or inheritance, for example when the model is shared mutable state.

What if a JSON key is a Swift keyword?

It is wrapped in backticks (`default`, `class`), which is legal Swift, and the CodingKeys entry maps it back to the original wire name.

Free & private — why use this JSON to Swift Codable

The JSON to Swift Codable runs 100% client-side in your browser. Your data is never uploaded to a server, no account is required, and the tool is completely free. It works offline once the page has loaded and is part of a growing collection of privacy-first developer utilities.

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