Is my JSON data uploaded to a server?

No. The conversion runs entirely in your browser with JavaScript. Nothing is sent over the network, which makes the tool safe for sensitive data.

What does the generated output look like?

The tool emits export type X = {...} declarations, with a syntax very close to TypeScript, one type per nested object.

Who is this tool for?

It is mainly useful for legacy React codebases that still use Flow and need types for new API payloads.

100% local — your data never leaves your browser

JSON to Flow Types Converter — Free Online Tool

Convert JSON to Flow type definitions instantly in your browser. Free, private and offline-friendly: your data never leaves your device.

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Root name

JSON input

Flow output

Why convert JSON to Flow?

Many legacy React codebases still rely on Flow for static typing. Paste a sample JSON payload above and get ready-to-use Flow type definitions in milliseconds, without writing them by hand.

How it works

The converter parses your JSON locally and emits export type X = {...} declarations, with a syntax close to TypeScript. Each nested object becomes its own exported type, referenced from the parent.

Frequently asked questions

Is my JSON data uploaded to a server?: No. The conversion runs entirely in your browser with JavaScript. Nothing is sent over the network, which makes the tool safe for sensitive data.
What does the generated output look like?: The tool emits export type X = {...} declarations, with a syntax very close to TypeScript, one type per nested object.
Who is this tool for?: It is mainly useful for legacy React codebases that still use Flow and need types for new API payloads.