# Custom Scalars

Gato GraphQL supports custom scalars, and makes available several standard custom scalar types to be used in your application.

## List of Custom Scalars

In addition to those that appear via introspection (i.e. in the GraphiQL and Interactive Schema clients), the following custom scalar types are available in the GraphQL schema:

### `Domain`

Domain scalar, such as `https://mysite.com` or `http://www.mysite.org`

### `IP`

IP scalar, including both IPv4 (such as `192.168.0.1`) and IPv6 (such as `2001:0db8:85a3:08d3:1319:8a2e:0370:7334`

### `IPv4`

IPv4 scalar, such as `192.168.0.1`

### `IPv6`

IPv6 scalar, such as `2001:0db8:85a3:08d3:1319:8a2e:0370:7334`

### `MACAddress`

MAC (media access control) address scalar, such as `00:1A:C2:7B:00:47`

### `PositiveFloat`

A positive float or 0

### `PositiveInt`

A positive integer or 0

### `PhoneNumber`

Phone number scalar, such as `+1-212-555-0149`

### `StrictlyPositiveFloat`

A positive float (> 0)

### `StrictlyPositiveInt`

A positive integer (> 0)

### `StringValueJSONObject`

A JSON Object where values are strings.

### `UUID`

UUID (universally unique identifier) scalar, such as `25770975-0c3d-4ff0-ba27-a0f98fe9b052`

## Introspection

When installing the Gato GraphQL plugin, these custom scalars will be available to be used in your application.

However, please notice that currently they are not referenced anywhere in the WordPress GraphQL schema, and as such they do not appear on the clients (GraphiQL and Interactive Schema). This is because a custom scalar type must be referenced to appear on the GraphQL schema, as [defined by the spec for built-in scalars](https://spec.graphql.org/October2021/#sec-Scalars.Built-in-Scalars):

> When returning the set of types from the `__Schema` introspection type, all referenced built-in scalars must be included. If a built-in scalar type is not referenced anywhere in a schema (there is no field, argument, or input field of that type) then it must not be included.