An HTML form with a required input field:
The <required> tag is supported in Internet Explorer 10, Firefox, Opera, and Chrome.
Note: The required attribute of the <input> tag is not supported in Internet Explorer 9 and earlier versions, or in Safari.
The required attribute is a boolean attribute.
When present, it specifies that an input field must be filled out before submitting the form.
Note: The required attribute works with the following input types: text, search, url, tel, email, password, date pickers, number, checkbox, radio, and file.
The required attribute is new in HTML5.
In XHTML, attribute minimization is forbidden, and the required attribute must be defined as <input required="required" />.
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