Suggestions and Option Groups

Use datalist for suggestions and optgroup for categories inside an enforced choice.

Datalist suggests without restricting

Optgroup organizes a fixed set of options

Choose by behavior

A datalist keeps the input editable; its options are suggestions.
A select limits submission to one of its available options.
An optgroup label helps users scan a long select without becoming selectable itself.

Important HTML

Datalist suggests values without restricting input; optgroup organizes categories inside a select.

<input id="resource-search" list="resource-suggestions">
<datalist id="resource-suggestions">
  <option value="Accessible forms"></option>
  …
</datalist>
<select id="session" name="session">
  <optgroup label="HTML">
    <option value="forms">Accessible forms</option>
  </optgroup>
</select>