default

The default keyword specifies a default JSON value that can be used when an instance value is not provided. It is commonly used in configuration schemas, form generation, and API documentation.

Syntax

The value of default can be of any type, including null. There are no restrictions on the value.

{
  "default": <any JSON value>
}

Purpose

The default keyword is a metadata annotation that:

Supplies a default value when no value is provided
Helps tools generate forms with pre-filled values
Documents the recommended or typical value for a field
Can be used by implementations to fill in missing values
Has no effect on validation (it is purely informational)
Should be a valid value against the associated schema (recommended)

Behavior

When multiple occurrences of the default keyword are applicable to a single sub-instance, implementations should remove duplicates. Implementations may use the default value as an additional example for documentation purposes.

Examples

Basic Default Values

{
  "type": "integer",
  "title": "Port",
  "description": "Server port number",
  "default": 8080,
  "minimum": 1,
  "maximum": 65535
}

The default port is 8080, which will be used if no port is specified.

String Default

{
  "type": "string",
  "title": "Environment",
  "enum": ["development", "staging", "production"],
  "default": "development"
}

Defaults to “development” environment when not specified.

Boolean Default

{
  "type": "boolean",
  "title": "Enable Logging",
  "description": "Enable detailed application logging",
  "default": true
}

Logging is enabled by default.

Object with Default Values

{
  "type": "object",
  "title": "Database Configuration",
  "properties": {
    "host": {
      "type": "string",
      "default": "localhost"
    },
    "port": {
      "type": "integer",
      "default": 5432
    },
    "database": {
      "type": "string",
      "default": "myapp"
    },
    "ssl": {
      "type": "boolean",
      "default": false
    }
  }
}

Each property has its own default value, providing a complete default configuration.

Array Default

{
  "type": "array",
  "title": "Allowed Origins",
  "description": "CORS allowed origins",
  "items": {
    "type": "string"
  },
  "default": ["http://localhost:3000"]
}

Defaults to allowing localhost origin.

Null Default

{
  "type": ["string", "null"],
  "title": "Middle Name",
  "description": "User's middle name (optional)",
  "default": null
}

Defaults to null when no middle name is provided.

Configuration Schema

{
  "type": "object",
  "title": "Application Settings",
  "properties": {
    "server": {
      "type": "object",
      "properties": {
        "port": {
          "type": "integer",
          "default": 3000
        },
        "host": {
          "type": "string",
          "default": "0.0.0.0"
        }
      }
    },
    "logging": {
      "type": "object",
      "properties": {
        "level": {
          "type": "string",
          "enum": ["debug", "info", "warn", "error"],
          "default": "info"
        },
        "format": {
          "type": "string",
          "enum": ["json", "text"],
          "default": "json"
        }
      }
    },
    "cache": {
      "type": "object",
      "properties": {
        "enabled": {
          "type": "boolean",
          "default": true
        },
        "ttl": {
          "type": "integer",
          "description": "Cache time-to-live in seconds",
          "default": 3600
        }
      }
    }
  }
}

A complete configuration schema with sensible defaults for all settings.

Pagination Parameters

{
  "type": "object",
  "title": "Pagination Options",
  "properties": {
    "page": {
      "type": "integer",
      "description": "Page number to retrieve",
      "minimum": 1,
      "default": 1
    },
    "pageSize": {
      "type": "integer",
      "description": "Number of items per page",
      "minimum": 1,
      "maximum": 100,
      "default": 20
    },
    "sortBy": {
      "type": "string",
      "description": "Field to sort by",
      "default": "createdAt"
    },
    "sortOrder": {
      "type": "string",
      "enum": ["asc", "desc"],
      "default": "desc"
    }
  }
}

API pagination with sensible defaults for common use cases.

Theme Configuration

{
  "type": "object",
  "title": "Theme Settings",
  "properties": {
    "mode": {
      "type": "string",
      "enum": ["light", "dark", "auto"],
      "default": "auto"
    },
    "primaryColor": {
      "type": "string",
      "pattern": "^#[0-9a-fA-F]{6}$",
      "default": "#007bff"
    },
    "fontSize": {
      "type": "string",
      "enum": ["small", "medium", "large"],
      "default": "medium"
    },
    "borderRadius": {
      "type": "integer",
      "description": "Border radius in pixels",
      "minimum": 0,
      "default": 4
    }
  }
}

UI theme settings with reasonable defaults.

Feature Flags

{
  "type": "object",
  "title": "Feature Flags",
  "properties": {
    "enableBetaFeatures": {
      "type": "boolean",
      "description": "Enable experimental beta features",
      "default": false
    },
    "enableAnalytics": {
      "type": "boolean",
      "description": "Enable usage analytics tracking",
      "default": true
    },
    "enableNotifications": {
      "type": "boolean",
      "description": "Enable push notifications",
      "default": true
    },
    "maxUploadSize": {
      "type": "integer",
      "description": "Maximum file upload size in MB",
      "minimum": 1,
      "maximum": 100,
      "default": 10
    }
  }
}

Feature flags with safe defaults.

Retry Configuration

{
  "type": "object",
  "title": "Retry Policy",
  "properties": {
    "maxRetries": {
      "type": "integer",
      "description": "Maximum number of retry attempts",
      "minimum": 0,
      "maximum": 10,
      "default": 3
    },
    "initialDelay": {
      "type": "integer",
      "description": "Initial delay in milliseconds",
      "minimum": 100,
      "default": 1000
    },
    "maxDelay": {
      "type": "integer",
      "description": "Maximum delay in milliseconds",
      "minimum": 1000,
      "default": 30000
    },
    "backoffMultiplier": {
      "type": "number",
      "description": "Exponential backoff multiplier",
      "minimum": 1,
      "default": 2
    }
  }
}

Retry policy with standard exponential backoff defaults.

Search Options

{
  "type": "object",
  "title": "Search Parameters",
  "properties": {
    "query": {
      "type": "string",
      "description": "Search query string"
    },
    "caseSensitive": {
      "type": "boolean",
      "default": false
    },
    "matchWholeWord": {
      "type": "boolean",
      "default": false
    },
    "includeArchived": {
      "type": "boolean",
      "default": false
    },
    "maxResults": {
      "type": "integer",
      "minimum": 1,
      "maximum": 1000,
      "default": 100
    }
  },
  "required": ["query"]
}

Search configuration with user-friendly defaults.

Best Practices

Use Valid Defaults

Ensure default values validate against the schema:

{
  "type": "integer",
  "minimum": 1,
  "maximum": 100,
  "default": 10
}

Choose Safe Defaults

Select defaults that are safe for production use:

{
  "type": "boolean",
  "title": "Debug Mode",
  "description": "Enable debug mode (should be false in production)",
  "default": false
}

Document Default Behavior

Combine default with description to explain the default choice:

{
  "type": "integer",
  "title": "Connection Timeout",
  "description": "Connection timeout in milliseconds. Default is 30 seconds, which is suitable for most network conditions.",
  "minimum": 1000,
  "default": 30000
}

Core Keywords

Applicator Keywords

Validation Keywords

Meta-Data

Syntax

Purpose

Behavior

Examples

Basic Default Values

String Default

Boolean Default

Object with Default Values

Array Default

Null Default

Configuration Schema

Theme Configuration

Feature Flags

Retry Configuration

Search Options

Best Practices

Use Valid Defaults

Choose Safe Defaults

Document Default Behavior

​Syntax

​Purpose

​Behavior

​Examples

​Basic Default Values

​String Default

​Boolean Default

​Object with Default Values

​Array Default

​Null Default

​Configuration Schema

​Pagination Parameters

​Theme Configuration

​Feature Flags

​Retry Configuration

​Search Options

​Best Practices

​Use Valid Defaults

​Choose Safe Defaults

​Document Default Behavior

Syntax

Purpose

Behavior

Examples

Basic Default Values

String Default

Boolean Default

Object with Default Values

Array Default

Null Default

Configuration Schema

Pagination Parameters

Theme Configuration

Feature Flags

Retry Configuration

Search Options

Best Practices

Use Valid Defaults

Choose Safe Defaults

Document Default Behavior