Browser wars revisited: The new rules for favicon Icons

Favicons are a big thing again, as every mobile browser reinvents the wheel and in it's own genious and individual way. Try to solve the favicon-quiz on css-tricks.com. You will have fun. 

The easiest way is to use a favicon generator like realfavicongenerator.net and check the result using a favicon checker.

Drupal really adds a favicon link, which is depreciated. In Drupal 8 you can remove favicon link using a Page_attached_alter:

/**
 * Implements template_preprocess_html().
 *
 * Search the head elements for the Favicon and remove it.
 * See: http://realfavicongenerator.net/faq#why_ico_not_declared.
 */
function YOUR_THEME_page_attachments_alter(&$page) {
  foreach ($page['#attached'] as $key => $element) {
    if ($key === 'html_head_link' && !empty($element)) {
      foreach ($element as $k => $item) {
        if (isset($item[0]['rel']) && $item[0]['rel'] === 'shortcut icon') {
          unset($page['#attached']['html_head_link'][$k]);
        }
      }
    }
  }
}

Check my answer for Drupal 8 on: Stackoverflow