function twentyseventeen_body_classes( $classes ) {
  // Add class of group-blog to blogs with more than 1 published author.
  if ( is_multi_author() ) {
    $classes[] = 'group-blog';
  }

  // Add class of hfeed to non-singular pages.
  if ( ! is_singular() ) {
    $classes[] = 'hfeed';
  }

  // Add class if we're viewing the Customizer for easier styling of theme options.
  if ( is_customize_preview() ) {
    $classes[] = 'twentyseventeen-customizer';
  }

  // Add class on front page.
  if ( is_front_page() && 'posts' !== get_option( 'show_on_front' ) ) {
    $classes[] = 'twentyseventeen-front-page';
  }

  // Add a class if there is a custom header.
  if ( has_header_image() ) {
    $classes[] = 'has-header-image';
  }

  // Add class if sidebar is used.
  if ( is_active_sidebar( 'sidebar-1' ) && ! is_page() ) {
    $classes[] = 'has-sidebar';
  }

  // Add class for one or two column page layouts.
  if ( is_page() || is_archive() ) {
    if ( 'one-column' === get_theme_mod( 'page_layout' ) ) {
      $classes[] = 'page-one-column';
    } else {
      $classes[] = 'page-two-column';
    }
  }

  // Add class if the site title and tagline is hidden.
  if ( 'blank' === get_header_textcolor() ) {
    $classes[] = 'title-tagline-hidden';
  }

  // Get the colorscheme or the default if there isn't one.
  $colors    = twentyseventeen_sanitize_colorscheme( get_theme_mod( 'colorscheme', 'light' ) );
  $classes[] = 'colors-' . $colors;

  return $classes;
}