A boolean value is one that evaluates to either true or false. The list of false values is indicated below. All other values are true. If a default value is specified in the attribute definition and the attribute is not declared in the HTML or specified as empty (e.g., attribute=”), then the default is used.

Attribute values that evaluate to false:

  • unspecified attribute
  • blank or empty
  • 0 (digit ‘0’)
  • f (letter ‘f’, case insensitive)
  • false (case insensitive)