Make Interest Groupings a required field

If you include an interest grouping in your sign-up form using checkboxes, you may want to enforce your visitors to select at least one interest.

There are multiple ways to go about this. As a start, you can pre-select one of the choices. To do this, you can add a “checked” attribute to the input field which you want to preselect.

In the following example, the input field for “Group 2” has an additional checked attribute. This will preselect that option when the page is loaded.

    <label>Checkbox Groups</label><br />
    <label><br />
        <input name="INTERESTS[c503c0f57d][]" type="checkbox" value="0f8a0ed3bd"> <span>Group 1</span><br />
    </label><br />
    <label><br />
        <input name="INTERESTS[c503c0f57d][]" type="checkbox" value="9446882237" checked> <span>Group 2</span><br />
    </label><br />
    <label><br />
        <input name="INTERESTS[c503c0f57d][]" type="checkbox" value="c12429b8e8"> <span>Group 3</span><br />

Another option is to use the following piece of JavaScript in your sign-up form. Whenever the form is submitted, this piece of code will ensure that at least one interest grouping was selected.

jQuery('.mc4wp-form').on('submit', function(evt) {
  var checkboxFields = jQuery(this).find('[name^="INTERESTS"]');
  if( checkboxFields.length ) {
    // check if at least one field is required
    for(var i=0; i<checkboxFields.length; i++) {
      if( checkboxFields[i].checked ) {
        return true;
    alert("Please select at least 1 interest group.");
    return false;

  return true;

Of course you can also combine the above two methods. A complete example can be found here.