HTML select vs input datalist

 You don’t know HTML Lists – Frank M Taylor

<select name="languages">

<optgroup label="Germanic">

<option value="en">English</option>

</optgroup>

<optgroup label="Romance">

<option value="fr">French</option>

<option value="es">Spanish</option>

<option value="pt">Portuguese</option>

</optgroup>

<optgroup label="Celtic">

<option value="en">Irish</option>

<option value="cy">Welsh</option>

</optgroup>

</select>

English French Spanish Portuguese Irish Welsh

<select name="languages" size="4" multiple>

<datalist id="languages">

<option>English</option>

<option>French</option>

<option>Spanish</option>

<option>Portuguese</option>

<option>Irish</option>

<option>Welsh</option>

<option>Hebrew</option>

<option>Arabic</option>

</datalist>

<input name="language" list="languages">

<datalist> HTML data list element - HTML | MDN