JSON to Python: generate Python classes from JSON

Paste an example, like an API response or a config file, and get Python dataclasses with type hints. Each nested object gets its own type, and lists of records are merged, so a field that only some items have comes out optional. Other languages: Go, Rust, Java, C#, Kotlin, Swift, Dart, Zod, and TypeScript.

How to use it

Paste JSON or open a file. A list of several records gives the best types.
The Python code appears as you type.
Copy it into your project or download it.

Private, local processing

This tool runs in your browser, in a background worker: nothing you paste or open is uploaded, and nothing is kept after you leave. For a list, types come from its first 1,000 items, which can be up to 5 MB of JSON. Already loaded features keep working if your connection drops. Loading another tool or jq for the first time needs a connection. When one tool isn't enough, GigaJSON opens your data with a tree, a table, JSONPath/JMESPath/jq queries, transforms, diff and history.

Questions

How are optional fields detected?

A key missing from some items gets the type str | None and the default None, so it goes after the required fields.

Which JSON library does the code use?

Only the standard library (dataclasses). json.load gives plain dicts, so build the objects yourself or with a library such as dacite.

Can I use a large file?

Yes. The file is read in a background worker, and the types come from the first 1,000 items of a list, which is plenty to find every field. That sample can be up to 5 MB of JSON.

What generates the code?

quicktype, the open-source generator (Apache 2.0), running in your browser. Check the result before you rely on it: a value that is always 0 in your examples is typed as a whole number, even if real data can have decimals.

Is my data uploaded?

No. The code is generated in your browser, so nothing you paste or open goes to a server, and nothing is kept after you leave the page.