JSON Schema Cheat Sheet — Validation Rules & Type Definitions
Essential keywords for validating JSON data structures, types, required keys, regular expressions, enum constraints, and arrays.
Core Validation Keywords
"type": "string" | "number" | "boolean" | "array" | "object" | "null"
Define the acceptable JSON primitive data type
"required": ["id", "email", "name"]
Array of property names that MUST be present on the target object
"properties": { "age": { "type": "integer", "minimum": 0 } }
Define schema validation rules for individual child keys
"additionalProperties": false
Reject any object payload containing undeclared keys
String Formats & Composition
"format": "email" | "uri" | "date-time" | "uuid"
Built-in semantic string validators for common data standards
"enum": ["admin", "editor", "viewer"]
Restrict value strictly to a predefined list of allowed choices
"oneOf": [{ ... }, { ... }]
Validate that the data matches EXACTLY ONE of the provided sub-schemas