Outputs a list of widget area IDs.

output-registered-sidebars.php

<?php
// Do NOT include the opening php tag shown above. Copy the code shown below.

add_action( 'wp_footer', 'prefix_list_widget_areas' );
/**
 * Outputs a list of widget area IDs.
 *
 * @since  1.0.0
 *
 * @return void
 */
function prefix_list_widget_areas() {

	foreach ( $GLOBALS['wp_registered_sidebars'] as $sidebar ) {

		echo $sidebar['id'] . '<br>';

	}

}