An HTML form with a pre-selected checkbox:
The checked attribute is a boolean attribute.
When present, it specifies that an <input> element should be pre-selected (checked) when the page loads.
The checked attribute can be used with <input type="checkbox"> and <input type="radio">.
The numbers in the table specify the first browser version that fully supports the attribute.
In XHTML, attribute minimization is forbidden, and the checked attribute must be defined as <input checked="checked" />.