Taxonomy term autocomplete

$form['tagtest'] = [
  '#type' => 'entity_autocomplete',
  '#target_type' => 'taxonomy_term',
  '#title' => 'Taxonomy Term',
];

// With default value
$form['tagtest'] = [
  '#type' => 'entity_autocomplete',
  '#target_type' => 'taxonomy_term',
  '#title' => 'Taxonomy Term',
  '#default_value' => \Drupal\taxonomy\Entity\Term::load(1),
];

// With a selected vocabulary.
$form['tagtest'] = [
  '#type' => 'entity_autocomplete',
  '#target_type' => 'taxonomy_term',
  '#title' => 'Taxonomy Term',
  '#selection_settings' => [
    'target_bundles' => ['tags'],
  ],
];

// Auto create a term if not exist.
$form['tagtest'] = [
  '#type' => 'entity_autocomplete',
  '#target_type' => 'taxonomy_term',
  '#title' => 'Taxonomy Term',
  '#autocreate' => [
    'bundle' => 'tags',  // Required. The bundle name for the new entity.
    'uid' => 1,  // Optional. The user ID for the new entity
  ],
];