HTML Guide for option

The W3C HTML validator issue arises when a <select> element is marked as required but doesn’t contain any <option> elements. The semantic purpose of a <select> element is to provide a list of options for the user to select from. If it is marked as required, it implies the user must make a selection from available options.

Here is an explanation of the involved elements and attributes:

• <select>: This represents a drop-down list in an HTML form.
  • required: When this attribute is present, it means the user must select an option before submitting the form. It cannot be empty.
  • multiple: This boolean attribute allows multiple selections if present.
  • size: This attribute specifies the number of visible options. If greater than 1 and multiple is not set, it turns the drop-down into a list box.

If the multiple attribute is not present and the size attribute is not greater than 1, you need at least one <option> element for the <select> to be valid when required is used.

To resolve this, ensure that your <select> element contains at least one <option>:

<label for="choices">Choose an option:</label>
<select id="choices" name="choices" required>
  <option value="">--Please choose an option--</option>
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
</select>

This example includes a placeholder option with an empty value to prompt the user to select an option and other valid options. The value for the placeholder is empty, which is a common practice for required fields to prevent it from being selected by default.

The selected attribute on option elements is boolean, so it should not have any value associated.

To fix this issue, simply remove the value assigned to the selected attribute.

Instead of this:

<select>
  <option selected="true">Option 1</option>
  <option>Option 2</option>
  <option>Option 3</option>
</select>

Use this:

<select>
  <option selected>Option 1</option>
  <option>Option 2</option>
  <option>Option 3</option>
</select>

In the example above, we’ve removed the value assigned to the selected attribute on the first option element. This will specify that “Option 1” is the default option to be selected in the dropdown list.

Drop-down lists can be defined in HTML by using the <select> tag, containing the different <option>s. Each <option> must have a name, which can be either contained between <option> and </option>, or alternatively using the label attribute.

Example:

<select name="size">
  <option value="s">small</option>
  <option value="m" label="medium"></option>
</select>

<select> elements that are required and are not multiple need a placeholder option that has no value, for example:

<select required>
  <option value="">choose size</option>
  <option value="s">small</option>
  <option value="l">large</option>
</select>

The <option> element no longer accepts a name attribute, which is now obsolete.

Example:

<select id="pet-select">
    <option value="">--Please choose an option--</option>
    <option value="dog">Dog</option>
    <option value="cat">Cat</option>
    <option value="hamster">Hamster</option>
</select>

A <select> element can only have multiple <option selected> if it includes the multiple attribute.

A <select> element represents a control that provides a menu of options. By default, only one option can be selected at a time unless the multiple attribute is present, allowing users to select more than one option. If multiple <option> elements use the selected attribute without multiple, this violates the HTML standard and triggers a validation error.

Example of incorrect usage:

<select name="color">
  <option value="red" selected>Red</option>
  <option value="green" selected>Green</option>
  <option value="blue">Blue</option>
</select>

Correct usage with only one selected option:

<select name="color">
  <option value="red" selected>Red</option>
  <option value="green">Green</option>
  <option value="blue">Blue</option>
</select>

Correct usage for multiple selected options with multiple attribute:

<select name="color" multiple>
  <option value="red" selected>Red</option>
  <option value="green" selected>Green</option>
  <option value="blue">Blue</option>
</select>

Remove duplicate selected attributes unless multiple is set, or add the multiple attribute if multiple selection is intended.