Online Tool Store
Swift Codable Generator
Paste a sample JSON object and generate matching Swift Codable structs, including nested types and CodingKeys enums for snake_case field names.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Example shown. Nested objects become nested structs; arrays of objects reuse the same generated type.
How the Swift Codable Generator works
- Paste a sample JSON object (or array of objects) into the left panel.
- The tool walks the JSON tree, inferring a Swift type for every field and generating one struct per object shape it encounters.
- Copy the generated Codable structs, including CodingKeys enums for any snake_case-to-camelCase renames.
Type inference rules
Strings map to String, whole numbers to Int, decimals to Double, booleans to Bool, objects to a nested Codable struct, and arrays to a Swift array of whichever type their elements resolve to.
FAQ
How does it handle snake_case JSON keys?
When a JSON key like "user_name" is converted to camelCase ("userName") for the Swift property, the tool automatically adds a CodingKeys enum mapping the property back to the original JSON key, so decoding still works correctly.
What happens with nested objects and arrays?
A nested object becomes its own separate Codable struct, named after the field it appeared under. An array of objects reuses that same generated struct as its element type; an array of primitives becomes a plain Swift array like [String] or [Int].
What if a field is null in my sample?
A null value is generated as an optional String? since the real type can't be inferred from a single null sample — edit the generated type by hand once you know what the field actually holds.
How we compare
| Feature | Online Tool Store | Xcode "Paste JSON as Code" | Writing structs by hand |
|---|---|---|---|
| No Xcode required | ✓ | ✗ | ✓ |
| Auto CodingKeys for snake_case | ✓ | ✓ | ✗ |
Type inference is based on a single JSON sample — always double-check optionality and numeric precision against your real API response before shipping.