How to get current language in html.html.twig of theme
Add the following snippet in your .theme file:

function MYTHEME_preprocess_html(&amp;$variables) {
  $variables['lang'] = \Drupal::languageManager()-&gt;getCurrentLanguage()-&gt;getId();
}


Then, in your html.html.twig file use:

{% if (lang == 'en') %}
  // Your action
{% endif %}