Types

YAML Schema supports validation for all YAML data types. This page covers number, integer, boolean, null, and array types. For strings, see Strings. For object validation, see Objects.

Number Types

Number Type

The number type validates both integers and floating-point numbers.

# Schema
type: number

Valid examples:

42

3.14

Invalid examples:

"I'm a string"

Integer Type

The integer type validates whole numbers. Note that 1.0 is considered an integer.

# Schema
type: integer

Valid examples:

42

-1

1.0

Invalid examples:

3.1415926

"42"

Number Constraints

Multiples

# Schema
type: number
multipleOf: 10

Valid examples:

0

10

20

Invalid examples:

23

Range Validation

# Schema
type: number
minimum: 0
exclusiveMaximum: 100

Valid examples:

0

10

99

Invalid examples:

-1

100

101

Note: minimum is inclusive, while exclusiveMaximum is exclusive.

Boolean Type

The boolean type validates true/false values.

# Schema
type: boolean

Valid examples:

true

false

Invalid examples:

"true"

Null Type

The null type validates only null values.

# Schema
type: null

Valid examples:

null

Invalid examples:

false

0

""

Array Type

The array type validates ordered lists of values.

Basic Array Validation

# Schema
type: array

Valid examples:

- 1
- 2
- 3
- 4
- 5

- 3
- different
- types: "of values"

Invalid examples:

Not: "an array"

Array Items

# Schema
type: array
items:
  type: number

Valid examples:

- 1
- 2
- 3
- 4
- 5

[]

Invalid examples:

- 1
- 2
- "3"
- 4
- 5

Note: A single non-matching item causes the entire array to be invalid. Empty arrays are always valid.

Tuple Validation with prefixItems

# Schema
type: array
prefixItems:
  - type: number
  - type: string
  - enum:
    - Street
    - Avenue
    - Boulevard
  - enum:
    - NW
    - NE
    - SW
    - SE

Valid examples:

- 1600
- Pennsylvania
- Avenue
- NW

- 10
- Downing
- Street

- 1600
- Pennsylvania
- Avenue
- NW
- Washington

Invalid examples:

- 24
- Sussex
- Drive

- Palais de l'Élysée

Additional Items

By default, additional items beyond prefixItems are allowed. You can restrict this:

# Schema
type: array
prefixItems:
  - type: number
  - type: string
items: false

Valid examples:

- 1600
- Pennsylvania
- Avenue
- NW

- 1600
- Pennsylvania
- Avenue

Invalid examples:

- 1600
- Pennsylvania
- Avenue
- NW
- Washington

You can also specify a schema for additional items:

# Schema
type: array
prefixItems:
  - type: number
  - type: string
items:
  type: string

Valid examples:

- 1600
- Pennsylvania
- Avenue
- NW
- Washington

Invalid examples:

- 1600
- Pennsylvania
- Avenue
- NW
- 20500

Contains

The contains keyword requires that at least one item in the array matches the schema:

# Schema
type: array
contains:
  type: number

Valid examples:

- life
- universe
- everything
- 42

- 1
- 2
- 3
- 4
- 5

Invalid examples:

- life
- universe
- everything
- forty-two

minItems and maxItems

# Schema
type: array
minItems: 2

Too few elements (including []) fails validation. maxItems rejects arrays longer than the limit; an empty array is always allowed when minItems is not set.

Combined with items:

type: array
minItems: 2
maxItems: 4
items:
  type: number

uniqueItems

When uniqueItems is true, no two elements may be equal (including strings). false allows duplicates. Empty and single-element arrays are always valid.

type: array
uniqueItems: true

minContains and maxContains

With contains, minContains (default 1) is the minimum number of elements that must match the contains schema; maxContains caps how many may match.

type: array
contains:
  type: number
minContains: 2

At least two numbers are required somewhere in the array.

type: array
contains:
  type: number
maxContains: 3

At most three elements may be numbers that satisfy contains.

Setting minContains: 0 means the contains constraint is satisfied even when no element matches (the array may have zero matches).