Boolean attribute (HTML)

A boolean attribute in HTML is an attribute that represents true or false values. If an HTML tag contains a boolean attribute — no matter the value of that attribute — the attribute is set to true on that element. If an HTML tag does not contain the attribute, the attribute is set to false.

If the attribute is present, it can have one of the following forms:

the attribute name alone; e.g., attribute, meaning its implicit value is the empty string the attribute with a value of the empty string; e.g., attribute=”” the attribute with a value of the attribute’s name itself, with no leading or trailing whitespace and case ignored; e.g., attribute=”attribute”, attribute=”ATTRIBUTE”