Form Select not rendering as a dropdown

Question

I'm building a form that contains a select but it's not rendering as a dropdown. It's rendering with a scrollbar and a dropdown down arrow

$form['my_select'] = [
  '#type' => 'select',
  '#empty_option' => '- None -',
  '#title' => $this->t('My Select'),
  '#options' => ['Option1', 'Option2'],
  '#size' => 6,
  '#weight' => '0',
];

What am I doing wrong?

Answer 1

It's rendering as a list because you have set #size to 6, which means 6 rows will be visible. Either remove the #size property completely, or set it to 1 to display a normal dropdown.

From the documentation:

#size: The number of rows in the list that should be visible at one time.