The Boolean required attribute, if present, indicates that the user must specify a value for the input before the owning form can be submitted.
The required attribute is supported by text, search, url, tel, email, password, date, month, week, time, datetime-local, number, checkbox, radio, file, <input> types along with the <select> and <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 image.
Note color and range don’t support required, but type color defaults to #000000, and range defaults to the midpoint between min and max — with min and max defaulting to 0 and 100 respectively in most browsers if not declared — so always has a value.
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 with the attribute is applied. So 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.
Note: Setting aria-required="true" tells a screen reader that an element (any element) is required, but has no bearing on the optionality of the element.
