JSON to PropTypes Converter Online

Generate React PropTypes.shape definitions from any JSON payload — isRequired, arrayOf, nested shapes, all inferred from a real sample. 100% in your browser.

Input JSON

PropTypes Output

What is a JSON to PropTypes converter?

A JSON to PropTypes converter reads a JSON sample and emits the React propTypes declaration that mirrors the JSON shape — PropTypes.string, PropTypes.number, PropTypes.arrayOf, PropTypes.shape, all marked .isRequired. The output drops straight under your functional or class component for development-time prop validation.

Hand-writing PropTypes for a deeply nested API response is tedious — every nested object needs its own PropTypes.shape({...}), every array needs arrayOf. OpenFormatter walks the JSON tree, infers the propTypes recursively, and runs entirely in your browser so internal API responses never leave your machine.

How to generate PropTypes from JSON — 4 steps

Paste a representative JSON sample. The propTypes will exactly match the field names and types in the sample — pick the JSON your component actually consumes.
Click Convert. The tool emits MyComponent.propTypes = { ... } with shapes, arrayOf, and isRequired automatically applied.
Copy under your component. Rename MyComponent to your component name. Make sure import PropTypes from 'prop-types' is at the top of the file.
Drop optional .isRequired. Remove .isRequired from any prop that callers may omit. PropTypes warn in development only.

JSON to PropTypes example

Sample JSON

{
  "id": 42,
  "name": "Ada Lovelace",
  "active": true,
  "address": { "city": "London" },
  "tags": ["admin", "engineer"]
}

Generated PropTypes

import PropTypes from 'prop-types';

MyComponent.propTypes = {
  id: PropTypes.number.isRequired,
  name: PropTypes.string.isRequired,
  active: PropTypes.bool.isRequired,
  address: PropTypes.shape({
    city: PropTypes.string
  }).isRequired,
  tags: PropTypes.arrayOf(PropTypes.string).isRequired
};

PropTypes.shape

Nested objects become inline PropTypes.shape({...}) — exactly what the prop-types runtime check expects, with isRequired flags on every observed key.

arrayOf inference

Arrays become PropTypes.arrayOf(PropTypes.string) or PropTypes.arrayOf(PropTypes.shape({...})) — type inferred from the first element.

Client-Side Only

JSON is parsed in JavaScript inside the browser. Internal API responses, tokens, or PII never reach a server.

Common use cases

check_circleAdding development-time prop validation to a JS-only React app without TypeScript
check_circlePublishing a React component library where consumers may not use TypeScript
check_circleGenerating PropTypes during a TypeScript migration as a temporary documentation layer
check_circleDocumenting an existing component with a real API response shape
check_circleCatching runtime prop bugs in a Storybook component playground
check_circleModelling Redux store slices that hydrate from a backend JSON payload
check_circleGenerating prop validation for components consuming third-party REST APIs
check_circleValidating context provider value shapes in a multi-component React tree

Why client-side generation matters

The JSON you paste often contains real customer data, OAuth tokens, signed URLs, or internal field names you do not want indexed by a third-party converter. OpenFormatter generates the PropTypes entirely in JavaScript on your device — open the Network tab in DevTools and you will see zero requests when you click Convert. Safe for enterprise React work, safe behind a corporate proxy, safe when the API contract is itself confidential.

Need other React tooling?

Generate TypeScript interfaces, Flow types, or browse other JSON converters — all browser-side.

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Frequently Asked Questions

Are PropTypes still recommended in 2026?

PropTypes are considered a legacy runtime check — TypeScript is the recommended choice for new React code because it catches errors at compile time and provides editor autocomplete. PropTypes remain useful for plain-JavaScript codebases without a TypeScript build step, libraries that publish JS so consumers without TS still get prop validation in development, and incremental migration projects where types live in JSDoc.

Why generate PropTypes from JSON?

Most React components consume API responses as their props. Hand-writing PropTypes.shape({...}) for a 30-field user object is tedious; this tool walks the JSON sample and emits the matching shape with arrayOf, nested shapes, and isRequired in one step. Paste the API response, copy the PropTypes block straight into your component file.

Does the prop-types package still ship?

Yes — prop-types is maintained on npm and works with React 18 and React 19. React removed PropTypes from the core React package in 16.3 (so you have to install prop-types separately), but the package itself is stable and not deprecated. PropTypes checks run only in development; they are stripped from production builds by tools like webpack’s DefinePlugin.

How are nested objects handled?

Each nested object becomes a PropTypes.shape({...}) inline. The shape function takes a literal mapping of fieldName → PropTypes.X. Deeply nested objects produce nested shape() calls; the indentation is generated automatically. For shapes that you want to reuse across multiple components, extract the shape into a const sharedShape = PropTypes.shape({...}).

What about arrays of objects?

PropTypes.arrayOf(PropTypes.shape({...})) — the generator emits this automatically when it sees an array of objects. The shape is inferred from the first element. For mixed-type arrays use PropTypes.arrayOf(PropTypes.oneOfType([PropTypes.string, PropTypes.number])) by hand.

Why is everything marked isRequired?

Because every key was present in the sample, the generator assumes the field is always required. If a prop is optional in your contract, drop the .isRequired suffix after pasting. PropTypes only warns in development when a required prop is missing — it does not block render.

Is the JSON uploaded to your servers?

No. Conversion runs entirely in your browser via JavaScript. Open DevTools → Network and click Convert — no requests are made. Pasting JSON containing tokens or proprietary data never leaves your machine.

Should I migrate to TypeScript instead?

For new components, yes — TypeScript catches errors before the code runs and gives editor autocomplete. PropTypes are best for libraries that ship JS, codebases without a TypeScript build pipeline, or as a first migration step. Generate both with our JSON-to-TypeScript tool and pick whichever fits your project.