Indicating required form controls using label or legend

Using text to indicate required state

The text field in the example below has the explicit label of "First name (required):". The label element's for attribute matches the id attribute of the input element and the label text indicates that the control is required.

<label for="firstname">First name (required):</label> 
<input id="firstname" name="firstname" type="text">

Using an asterisk to indicate required state

The text field in the example below has an explicit label that includes an asterisk to indicate the control is required. It is important that the asterisk meaning is defined at the start of the form. In this example, the asterisk is contained within a abbr element to allow for the asterisk character to be styled so that it is larger than the default asterisk character, since the asterisk character can be difficult to see for those with impaired vision.

.req {font-size: 150%}

<p>Required fields are marked with an asterisk
   (<abbr class="req" title="required">*</abbr>).</p>
<form action="https://example.com" method="post">
  <label for="firstname">First name <abbr class="req" title="required">*</abbr>:</label> 
  <input id="firstname" name="firstname" type="text">
  ...
</form>

Using an image to indicate required state

The text field in the example below has an explicit label that includes an image to indicate the control is required. It is important that the image meaning is defined at the start of the form.

<p><img alt="required" src="req_img.gif"> indicates that the information is required</p>
<form action="https://www.example.com" method="post">
  <label for="firstname">First name <img alt="required" src="req_img.gif">:</label> 
  <input id="firstname" name="firstname" type="text">
  ...
</form>

Indicating required state for groups of radio buttons or check box controls

Radio buttons and checkboxes are treated differently than other interactive controls since individual radio buttons and checkboxes are not required but indicates that a response for the group is required. The methods used in examples 1-3 apply to radio buttons and checkboxes, but the indication of the required state should be placed in the legend element instead of the label element.

<fieldset>
  <legend>I am interested in the following (Required):</legend>
  <div>
    <input id="photo" name="interests" type="checkbox" value="ph">
    <label for="photo">Photography</label>
  </div>
  <div>
    <input checked id="watercol" name="interests" type="checkbox" value="wa">
    <label for="watercol">Watercolor</label>
  </div>
  <div>
    <input checked id="acrylic" name="interests" type="checkbox" value="ac">
    <label for="acrylic">Acrylic</label>
  </div>
  ...
</fieldset>