code: public function getLocale()
      {
          if (!$this->cookiesLoaded) {
              $key = $this->cookiePrefix . 'lang_locale';
              $queuedCookieLocale = \Cookie::queued($key, null);
              $locale = getSupportedLocale($queuedCookieLocale != null ? $queuedCookieLocale->getValue() : \Cookie::get($key, ''));
              parent::setLocale($locale);
              
              // load unpublished translation flag at the same time
              $this->getShowUnpublished();
              $this->cookiesLoaded = true;
          }
          return parent::getLocale();
      }
docs: Get the default locale being used.
  
  @return string