JSON to JSON Schema

About this tool

A JSON Schema describes the shape data must take: which types are allowed, which properties exist and which are required. Writing one by hand is tedious, so this tool infers a solid first draft from an example document.

Every object contributes its keys as properties and as required entries; arrays are described by the union of their elements, so a mixed array still gets a schema that accepts all of it. Integers and decimals are distinguished. The output targets Draft 2020-12 by default.

Inference has a built-in limit worth understanding: a schema can only describe what the example demonstrated. If a field happened to be null in your sample, it is typed as null; if an optional field was present, it is marked required. That is why the result is a first draft to tighten, not a finished contract — feed it a sample that covers the variations you care about, and it will get much closer.

The usual next steps are to relax `required` down to the genuinely mandatory fields, add `format` for emails, dates and URIs, add `enum` where a field only takes a few values, and add ranges with `minimum`, `maxLength` or `minItems`. Once tightened, validate real documents against it on the JSON Schema Validator page.

How to use this tool

1. 1

   Paste a representative JSON example, or upload a file.

2. 2

   Choose the JSON Schema draft you are targeting.

3. 3

   Press Generate schema.

4. 4

   Review and tighten the schema — add formats, patterns or descriptions — then copy or download it.

Key features

• Draft 2020-12, 2019-09 and Draft-07 output
• Required keys captured from the example
• Array item schemas merged across all elements
• Integer and number types distinguished
• Optional generated title field

Example

{"id":1,"name":"Ada","active":true}

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "id": { "type": "integer" },
    "name": { "type": "string" },
    "active": { "type": "boolean" }
  },
  "required": [ "active", "id", "name" ]
}

Good to know

Frequently asked questions

Further reading

How to validate JSON — There are two different questions hiding behind "is this JSON valid": does it parse, and does it match the shape it is supposed to have.