JSON Schema keywords and types

This page is a practical reference for configuring validation rules using JSON Schema in the Schema tab.
Here you'll find:

Supported JSON Schema keywords and format options.
Quick-reference tables for core keywords and standardized string formats.

Note!
Advanced custom schemas edited directly in the Schema tab may not be fully editable in the visual rules UI.

See:

JSON Schema reference - For details about formal definitions, interoperability considerations, keyword behaviors, and advanced topics.
JSON Schema reference - For detailed JSON Schema examples.

1 Type/keyword reference table
2 Common keywords
3 Advanced keywords
4 Grouping keywords
5 Format values

Type/keyword reference table

This table shows which JSON Schema keywords apply to each data type.

Data type	Relevant keywords	Usage

Data type	Relevant keywords	Usage
array	items, minItems, maxItems, uniqueItems	Control array content, length, and uniqueness
number	minimum, maximum, exclusiveMinimum, exclusiveMaximum, multipleOf	Control allowed value ranges and divisibility
object	properties, required, minProperties, maxProperties, patternProperties, additionalProperties, dependencies	Control object shape, requiredness, and property constraints
string	minLength, maxLength, pattern, format	Control length, pattern, and semantic format
grouping	allOf, anyOf, oneOf, not	Combine or negate multiple schemas/rules

Common keywords

These are the most frequently used keywords for basic validation tasks.

Keyword	Description	Schema usage example

Keyword	Description	Schema usage example
type	Specifies the data type	{ "type": "string" }
*properties (see the warning below this table)	Defines properties for an object	{ , "properties": { "name": { "type": "string" } } }
required	Lists required properties	{ "required": ["name", "email"] }
enum	Restricts values to a set	{ "type": "string", "enum": ["red", "green"] }
format	Standardized format for a string	{ "type": "string", "format": "email" }
pattern	String must match a regex	{ "type": "string", "pattern": "^[A-Z]{3}$" }
minLength	Minimum string length	{ "type": "string", "minLength": 2 }
maxLength	Maximum string length	{ "type": "string", "maxLength": 30 }
minimum	Minimum numeric value	{ "type": "number", "minimum": 10 }
maximum	Maximum numeric value	{ "type": "number", "maximum": 100 }
items	Schema for array items	{ "type": "array", "items": { "type": "string" } }
additionalProperties	Allow/disallow unspecified object fields	{ , "additionalProperties": false }

Caution!
When defining validation rules for nested fields, do not use dot notation (e.g., "foo.bar") in the properties keyword.

JSON Schema treats "foo.bar" as a single, literal property name, not as a path to a nested value.
To validate nested fields, you must use nested properties blocks:

Incorrect

Does not validate nested fields; it only matches an object with a property literally named "foo.bar"

{
  "properties": {
    "foo.bar": { "minimum": 5 }
  }
}

Correct

Validates the nested "bar" field inside "foo"; this matches an object like { "foo": { "bar": 6 } } and applies the rule to the nested "bar" property.

{
  "properties": {
    "foo": {
      "properties": {
        "bar": { "minimum": 5 }
      }
    }
  }
}

Note!
The Rules section in the UI does not support dot notation for nested fields and will display an error if used in the schema block. Always use the correct nested structure for validating nested fields.

For details on structuring nested objects, see Creating your first schema.

Advanced keywords

Useful for more complex validation and precise control over data.

Keyword	Description	Schema usage example

Keyword	Description	Schema usage example
patternProperties	Properties matching a regex	{ "patternProperties": { "^S_": { "type": "string" } } }
minItems	Minimum array length	{ "type": "array", "minItems": 2 }
maxItems	Maximum array length	{ "type": "array", "maxItems": 10 }
uniqueItems	All items in the array must be unique	{ "type": "array", "uniqueItems": true }
minProperties	Minimum number of object properties	{ , "minProperties": 1 }
maxProperties	Maximum number of object properties	{ , "maxProperties": 5 }
dependencies	Require other properties based on the presence of one	{ "dependencies": { "credit_card": ["billing_address"] } }
multipleOf	The number must be a multiple of the value	{ "type": "number", "multipleOf": 10 }
exclusiveMinimum	Value must be strictly greater than the minimum	{ "type": "number", "exclusiveMinimum": 0 }
exclusiveMaximum	Value must be strictly less than the maximum	{ "type": "number", "exclusiveMaximum": 100 }

Grouping keywords

These keywords let you combine or negate multiple rules, useful for complex validation logic.

Keyword	Description	Schema usage example

Keyword	Description	Schema usage example
allOf	Must match all schemas in the array	{ "allOf": [ { "type": "string" }, { "maxLength": 5 } ] }
anyOf	Must match at least one schema in the array	{ "anyOf": [ { "type": "string" }, { "type": "number" } ] }
oneOf	Must match exactly one schema in the array	{ "oneOf": [ { "type": "string" }, { "type": "number" } ] }
not	Must not match the specified schema	{ "not": { "type": "null" } }

Format values

The format keyword adds semantic meaning to strings and can enforce well-known formats like email, date or uri.

Format	Description	Schema usage example	Valid data example

Format	Description	Schema usage example	Valid data example
date-time	RFC3339 Date & Time	{ "type": "string", "format": "date-time" }	"2025-06-16T11:00:00Z"
date	Calendar Date	{ "type": "string", "format": "date" }	"2025-06-16"
time	Time of Day	{ "type": "string", "format": "time" }	"11:00:00"
email	Email Address	{ "type": "string", "format": "email" }	"user@example.com"
hostname	Internet Hostname	{ "type": "string", "format": "hostname" }	"Example Domain"
ipv4	IPv4 Address	{ "type": "string", "format": "ipv4" }	"192.168.1.1"
ipv6	IPv6 Address	{ "type": "string", "format": "ipv6" }	"2001:db8::1"
uri	URI	{ "type": "string", "format": "uri" }	"Example Domain "
uuid	UUID	{ "type": "string", "format": "uuid" }	"3e4666bf-d5e5-4aa7-b8ce-cefe41c7568a"