add_filter( 'wpseo_breadcrumb_single_link', 'ss_breadcrumb_single_link', 10, 2 );
function ss_breadcrumb_single_link( $link_output, $link ) {
$element = '';
$element = esc_attr( apply_filters( 'wpseo_breadcrumb_single_link_wrapper', $element ) );
$link_output = $element;
if ( isset( $link['url'] ) ) {
$link_output .= '<a rel="nofollow" href="' .
esc_url( $link['url'] ) . '" rel="v:url" property="v:title" class="my-class">' .
esc_html( $link['text'] ) . '</a>';
}
return $link_output;
}
this is a function.php code in this you can add the custom class to breadcrumbs