.JSON

JSON Schema

Introduction

JSON Schema is a JSON document that describes what other JSON documents must look like: which properties an object has, which are required, and what type and range each value may take. A validator checks a document against the schema, and editors use schemas to offer completion and show mistakes as you type.

Schemas are saved as ordinary .json files, often named *.schema.json. Many configuration files, such as package.json and tsconfig.json, have published schemas, and OpenAPI descriptions of web APIs use JSON Schema for their data types.

Structure

A schema is a JSON object, or true or false. Its keys are keywords. Common ones are:

  • $schema: the URL of the version of JSON Schema the file follows, such as https://json-schema.org/draft/2020-12/schema
  • $id: the schema’s own URL, and $ref to point at another schema or part of one
  • type: object, array, string, number, integer, boolean or null
  • properties and required for objects, and items for arrays
  • enum, minimum, maxLength, pattern and others that limit values
  • allOf, anyOf, oneOf and not to combine schemas

Several drafts of the standard are in use, and the $schema value says which one a file follows. Draft-07 and 2020-12 are the most common.

Also used for

Links

Software

Developers

Reference