Which JSON Schema draft does this generate?

The output targets draft-07, using "$schema": "http://json-schema.org/draft-07/schema#", type, properties, items, and required — the keywords supported by most validators like AJV.

How does it decide which fields are required?

With "Mark present keys as required" checked, a key is required only if it appears in every object at that position. When the sample is a single object, all of its keys are required. When the sample is an array of objects, a key must appear in every item to be required.

How are numbers handled?

Whole numbers are typed as "integer" and numbers with a decimal part are typed as "number", matching the JSON Schema convention that integer is a stricter subset of number.

What happens if a field has different types across array items, like a string in one item and a number in another?

The generated type becomes an array of the observed types, for example ["string","integer"], which is valid JSON Schema syntax for a property that accepts more than one type.

Does "additionalProperties: false" apply to every nested object?

Yes. When enabled, the option is applied recursively to every object in the schema, not just the top level, so no object in the structure accepts extra keys.

Is my JSON sent to a server?

No. Parsing and schema generation run entirely in your browser with plain JavaScript. Your data never leaves your device.

JSON to JSON Schema

Name: JSON to JSON Schema
Availability: InStock
Author: Nham Vu

Paste a sample JSON object or array and get a matching draft-07 JSON Schema with inferred types, nested structure, and required fields.

Sample JSON

Schema title

Mark present keys as required

Disallow additional properties

JSON Schema Output

Paste sample JSON and click Generate Schema

Copied!

Summary

Paste a sample JSON object or array and get a matching draft-07 JSON Schema with inferred types, nested structure, and required fields.

How it works

Paste a sample JSON object or array into the input panel, or load the example.
Choose whether present object keys should be marked required and whether extra properties should be disallowed.
Click Generate Schema to infer types for every property, including nested objects and arrays.
When the sample is an array, items are merged so a field that only appears in some items is not marked required.
Review the generated draft-07 JSON Schema in the output panel.
Click Copy or Download to save the schema.

Use cases

Turn a sample API response into a JSON Schema for request or response validation.
Draft a starting schema for a config file from a working example.
Generate a schema to plug into an AJV, Zod, or JSON Schema based validator.
Document the shape of a JSON payload for a teammate or API consumer.
Check which fields are optional across an array of JSON records before writing validation rules.
Bootstrap form validation rules from a sample JSON payload.

Frequently Asked Questions

Last updated: 2026-07-24 · Reviewed by Nham Vu