get_previewable_devices(); foreach ( $previewed_devices as $device => $params ) { if ( isset( $params['default'] ) && true === $params['default'] ) { $previewed_device_name = $device; break; } } if ( $previewed_device_name ) { $wp_customize->set_preview_url( add_query_arg( 'customize_previewed_device', $previewed_device_name, $wp_customize->get_preview_url() ) ); } }