JSON Schema is a vocabulary for defining the structure and validation rules of JSON data. It specifies field types, required properties, value constraints, and patterns. It's written in JSON itself and used for API validation, documentation, and code generation.

How do I validate JSON against a schema?

Use a JSON Schema validation library for your language — AJV for JavaScript, jsonschema for Python, gojsonschema for Go. Pass your data and schema to the validator, and it returns whether the data conforms and what errors exist.

What is the difference between anyOf and oneOf?

anyOf passes if the data matches at least one of the listed schemas. oneOf passes only if the data matches exactly one schema — if it matches two or more, validation fails. Use oneOf for discriminated unions where exactly one variant should match.

Can JSON Schema validate nested objects?

Yes. You define nested schemas by placing object schemas inside the properties of a parent object schema. You can also use $ref to reference shared schema definitions and avoid duplication.

JSON Schema Validation: The Complete Guide

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