Validate JSON data with schemas, types, required fields, formats, composition, and API contracts.
Lessons
Avoid the pitfalls beginners hit most often.
Common JSON Schema Mistakes is easiest to learn by reading the example, changing it, and observing the result.
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"$id": "https://example.com/schemas/lesson.json",
"title": "Lesson",
"type": "object",
"required": ["slug", "title"],
"properties": {
"slug": { "type": "string", "pattern": "^[a-z0-9-]+$" },
"title": { "type": "string", "minLength": 3, "maxLength": 80 },
"minutes": { "type": "integer", "minimum": 1 },
"level": { "type": "string", "enum": ["beginner", "advanced"] },
"tags": { "type": "array", "items": { "type": "string" }, "uniqueItems": true }
},
"additionalProperties": false
}Practice the Common JSON Schema Mistakes example in a small scratch file, then explain what changed and why.