JSON to Code
Generate Go, Rust, Python, Java, Kotlin, C# and TypeScript types from JSON.
Your JSON is parsed and converted to code entirely in your browser, so nothing is uploaded to a server.
Need only TypeScript types? Try the JSON to TypeScript converter.
About JSON to Code
This json to code generator turns a sample JSON payload into ready-to-use type definitions for Go, Rust, Python, TypeScript, Java, Kotlin and C#. Paste an API response and instantly get a json to go struct, a json to typescript interface, a json to rust serde model, a json to python dataclass or Pydantic model, or a json to java class. It infers field types, marks optional keys, names nested structs, and handles arrays of objects so you spend less time hand-writing boilerplate. Pick a target language, set the root type name, and copy or download the result. It is built for backend and frontend developers, API integrators and QA engineers who need to generate types from json quickly. Everything is processed locally in your browser, so your data never leaves your device.
Features
- Generates types for eight targets: Go, Rust (serde), Python dataclasses, Pydantic, TypeScript, Java, Kotlin and C#
- Infers primitive types, distinguishing integers from floating-point numbers
- Detects nested objects and emits a separate named struct for each one
- Handles arrays of objects by merging keys and marking fields missing from some items as optional
- Adds language-appropriate serialization annotations, like Go json tags and Rust derive(Serialize, Deserialize)
- Lets you set a custom root type name that drives the generated class and download file name
- Reports JSON parse errors with line and column so you can fix malformed input
- Copy the output or download it with the correct file extension for each language
How to use the JSON to Code
- Paste your JSON object or array of objects into the input box.
- Choose a target language from the dropdown, such as Go, TypeScript or Rust (serde).
- Set the Root name field to name the top-level type.
- Review the generated code in the output panel and check any parse error messages.
- Copy the code or download it as a file in the matching language extension.
Example
Input
{ "id": 1, "name": "Ada", "active": true }
Output
export interface Root {
id: number;
name: string;
active: boolean;
}
JSON converted to a TypeScript interface with the root type named Root.
Common errors & troubleshooting
- The tool reports a parse error with a line and column number. — Your JSON is invalid. Check for trailing commas, single quotes or unquoted keys, and ensure the input is strict JSON before generating.
- You see 'Top-level JSON must be an object or an array of objects.' — Wrap a bare value in an object, or pass an object or an array of objects. A top-level string, number or boolean cannot be turned into a type.
- Numbers that are whole come out as int or number but you expected a float. — Type inference is based on the sample value, so 9 becomes an integer and 9.5 a float. Include a decimal point in the sample if the field is really floating point.
- A field is unexpectedly marked optional. — When you pass an array of objects, any key missing from some items is treated as optional. Provide items that all contain the key if it should be required.
- An empty array produces an 'any' or 'unknown' element type. — The generator cannot infer an element type from an empty array. Include at least one representative element so the item type can be detected.
Frequently asked questions
- What is the JSON to Code generator?
- It is a browser-based tool that reads a sample JSON payload and writes matching type definitions for Go, Rust (serde), Python dataclasses, Pydantic, TypeScript, Java, Kotlin and C#, so you can drop typed models straight into your project.
- How do I generate a Go struct or TypeScript interface from JSON?
- Paste your JSON, pick Go or TypeScript from the language dropdown, set the Root name, then copy or download the generated struct or interface. The output updates as you type.
- How does JSON to Code handle nested objects and arrays?
- Each nested object becomes its own named struct or class, and arrays of objects are merged so the element type captures every key. Keys missing from some array items are marked optional.
- Can I convert a top-level JSON array?
- Yes. A top-level array of objects is supported: the tool emits the element type plus a Root alias such as type Root = []Item in Go or export type Root = Item[] in TypeScript.
- How are optional fields decided in the generated types?
- When you provide several objects in an array, any key that does not appear in every object is treated as optional and is emitted as nullable or optional in the target language.
- Is my JSON sent anywhere when I generate code?
- No. The JSON to Code generator runs entirely in your browser, your data never leaves your device.
Related tools
All ArrayKit tools