JSON to TypeScript Developer
Turn a JSON sample into TypeScript interfaces you can paste straight in.
JSON to TypeScript is a free online tool that turn a JSON sample into TypeScript interfaces you can paste straight in. It runs entirely in your web browser using plain JavaScript, so files are processed on your own device and never uploaded to a server. There is no sign-up, no file size limit imposed by the site, no watermark and no paid tier.
- Price
- Free — no account, no quota, no watermark
- Category
- Developer
- Where it runs
- In your browser, on your device
- Files uploaded
- None
- Technology
- plain JavaScript
- Settings
- 1
- Works offline
- Yes, after the first visit
About JSON to TypeScript
Interfaces are generated from a JSON sample by inferring each field's type. The limitation is inherent and worth stating plainly: a sample shows what was present once, not what is possible. A field that happened to be non-null in your sample is typed as non-nullable, and an empty array yields `unknown[]`. Treat the output as a strong first draft, then mark the optional fields yourself.
How to use it
- Paste the text you want to run through json to typescript.
- Set root name.
The one setting
| Setting | What it does | Default |
|---|---|---|
| Root name | Free text. | Root |
Under the hood
| Runs on | plain JavaScript — runs the whole thing |
| Controls | Root name |
Questions
Why is my optional field not marked optional?
Because it was present in the sample. Absence cannot be inferred from a single example — feed it several representative payloads, or add the `?` by hand where the API documentation says a field may be missing.
How are nested objects handled?
Each becomes its own named interface, referenced from the parent, rather than being inlined. That keeps the result readable and the pieces reusable.