How to increase meta tag description field to 320 characters?
I had to write a hook_page_attachments_alter for this

function mymodule_page_attachments_alter(array &amp;$page) {
  foreach($page['#attached']['html_head] as &amp;$html_head) {
    if($html_head[1] == 'description') {
      $html_head_content = $html_head[0]['#attributes']['content'];
      if(Unicode::strlen($html_head_content) &gt; 320) {
        $html_head[0]['#attributes']['content'] = Unicode::truncate($html_head_content, 320);
      }
    }
  }
}