Minimal object
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"type": "object",
"properties": {
"name": { "type": "string" },
"age": { "type": "integer", "minimum": 0 }
},
"required": ["name"]
}Enum / string pattern
{
"type": "object",
"properties": {
"status": { "type": "string", "enum": ["active", "paused", "closed"] },
"email": { "type": "string", "format": "email" },
"slug": { "type": "string", "pattern": "^[a-z0-9-]+$" }
}
}Array of items
{
"type": "array",
"minItems": 1,
"maxItems": 10,
"uniqueItems": true,
"items": {
"type": "object",
"properties": { "id": { "type": "integer" } },
"required": ["id"]
}
}Nested objects with $ref
{
"$defs": {
"address": {
"type": "object",
"properties": {
"street": { "type": "string" },
"zip": { "type": "string", "pattern": "^\\d{5}$" }
}
}
},
"type": "object",
"properties": {
"shipping": { "$ref": "#/$defs/address" },
"billing": { "$ref": "#/$defs/address" }
}
}oneOf — discriminated union
{
"oneOf": [
{ "type": "object", "properties": { "kind": { "const": "dog" }, "bark": { "type": "string" } }, "required": ["kind","bark"] },
{ "type": "object", "properties": { "kind": { "const": "cat" }, "meow": { "type": "string" } }, "required": ["kind","meow"] }
]
}Useful keywords
| type | string | number | integer | boolean | null | array | object |
|---|---|
| required | Array of required property names |
| additionalProperties | false to reject unknown keys |
| minLength / maxLength | String constraints |
| minimum / maximum | Number constraints (exclusiveMinimum / exclusiveMaximum for open) |
| format | date-time, email, uri, uuid, ipv4, ipv6 (validator-specific) |
| allOf / anyOf / oneOf | Combinators |
| const | Match single value exactly |
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