JSON to TypeScript
Paste a JSON sample and get clean TypeScript interfaces — nested objects, optional fields, and unions inferred. Runs entirely in your browser, no upload.
JSON to TypeScript interfaces, in your browser
Paste a JSON object or array and get ready-to-use TypeScript interfaces. Everything runs locally in your browser — your JSON is never uploaded.
What it infers
- Nested objects become their own named interfaces (keyed off the field name).
- Arrays of objects are merged: a key missing in some elements becomes
optional (
?), and differing value types become a union (e.g.number | string). - Primitives map to
string/number/boolean/null; empty arrays becomeany[]. - Non-identifier keys are quoted (
"first-name": string).
Options
- Root type name — names the top-level interface (default
Root). A top-level array yieldsexport type Root = RootItem[];. - Add 'export' — prefix declarations with
export(on by default).
FAQ
What happens when objects in an array don't all have the same keys?
They're merged structurally into one interface. A key that's missing from some
elements becomes optional (name?:), and a key whose values have different
types across elements becomes a union (id: number | string). The generated
interface therefore describes every element you pasted, not just the first one.
How are the interface names picked?
The top-level name comes from the Root type name option (PascalCased,
default Root). Nested objects are named after their field key — a user field
produces interface User — and elements of an array take the singular of the
array's key, so an items array yields interface Item. If two shapes would
claim the same name, a suffix keeps them distinct.
How are null values and empty arrays typed?
A JSON null maps to the TS type null; when the same key is null in one
sample and a string in another, you get string | null. An empty array carries
no element information, so it becomes any[] — paste a sample with at least one
element if you want a precise type.
Why did I get a type alias instead of an interface?
Objects become interface declarations, but a top-level array (or primitive)
can't be an interface, so the tool emits a type alias — e.g.
export type Root = RootItem[]; — alongside the interfaces for the element
shapes. Untick Add 'export' if you want bare declarations for pasting inside
an existing module.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool json-to-typescript '{ "name": "Ada", "roles": ["admin"] }'New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/json-to-typescript/?json=%7B%20%22name%22%3A%20%22Ada%22%2C%20%22roles%22%3A%20%5B%22admin%22%5D%20%7D&root_name=Root&export=trueMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.