required attribute, if present, indicates that the user must specify a value for the input before the owning form can be submitted.
required attribute is supported by
<input> types along with the
<textarea> form control elements. If present on any of these input types and elements, the
:required pseudo class will match. If the attribute is not included, the
:optional pseudo class will match.
The attribute is not supported or relevant to range and color, as both have default values. It is also not supported on hidden as it can not be expected that a user to fill out a form that is hidden. Nor is it supported on any of the button types, including
range don't support
required as both always have a value. Type
color defaults to
#000000. The default for
range is the midpoint between
max — with
max defaulting to 0 and 100 respectively in most browsers if not declared.
In the case of a same named group of radio buttons, if a single radio button in the group has the
required attribute, a radio button in that group must be checked, although it doesn't have to be the one on which the attribute is applied. To improve code maintenance, it is recommended to either include the
required attribute in every same-named radio button in the group, or else in none.
In the case of a same named group of checkbox input types, only the checkboxes with the
required attribute are required.
aria-required="true" tells a screen reader that an element (any element) is required, but has no bearing on the optionality of the element.