JSON to TypeScript

How to use it

1. Paste your JSON into the left panel — a sample payload loads on start.
2. Set the root interface name; nested interfaces are named from their key paths.
3. Toggle optional fields to mark keys that are missing in some sibling objects with ?.
4. The output updates as you type; click Copy to take the interfaces into your project.
5. Name collisions get numeric suffixes, and non-identifier keys are emitted as ['quoted-key'].

Common use cases

• API clients — generate request and response types from a real payload instead of writing them by hand.
• Config files — type your JSON settings file so edits are checked at compile time.
• Test fixtures — describe fixture shapes once and reuse them across test files.
• Learning type shapes — see how nested arrays of objects decompose into named interfaces.

Why it stays private

Parsing and code generation are local string operations; your JSON is never uploaded. Safe for internal payloads, tokens-free but unreleased API shapes, and customer data samples.

FAQ

Q: How are arrays of objects handled? A: All object elements are merged into one interface covering their key union; the array itself is typed as that interface name followed by []. Non-object elements contribute a union member when they differ.

Q: What happens to null values? A: null becomes the null type and joins any union, so a field that is string in one place and null in another comes out as string | null.

Q: Are identical nested shapes deduplicated? A: Not structurally — deduplication is by generated name only. Two objects with the same keys but different names produce two interfaces; merge them manually if you want a single shared type.