is_main_site() WordPress Function

function is_main_site( $site_id = null, $network_id = null ) {
	if ( ! is_multisite() ) {
		return true;
	}

	if ( ! $site_id ) {
		$site_id = get_current_blog_id();
	}

	$site_id = (int) $site_id;

	return get_main_site_id( $network_id ) === $site_id;
}
Uses	Description
wp-includes/functions.php:get_main_site_id()	Gets the main site ID.
wp-includes/load.php:is_multisite()	If Multisite is enabled.
wp-includes/load.php:get_current_blog_id()	Retrieve the current site ID.
Used By	Description
wp-includes/user.php:wp_schedule_update_user_counts()	Schedules a recurring recalculation of the total count of users.
wp-admin/includes/class-wp-ms-sites-list-table.php:WP_MS_Sites_List_Table::site_states()	Maybe output comma-separated site states.
wp-admin/includes/class-wp-site-health-auto-updates.php:WP_Site_Health_Auto_Updates::test_wp_version_check_attached()	Check if updates are intercepted by a filter.
wp-includes/option.php:delete_expired_transients()	Deletes all expired transients.
wp-admin/press-this.php:wp_load_press_this()
wp-includes/functions.php:_wp_upload_dir()	A non-filtered, non-cached version of wp_upload_dir() that doesn’t check the path.
wp-admin/includes/class-wp-ms-sites-list-table.php:WP_MS_Sites_List_Table::column_cb()	Handles the checkbox column output.
wp-admin/includes/upgrade.php:wp_should_upgrade_global_tables()	Determine if global tables should be upgraded.
wp-admin/includes/class-wp-automatic-updater.php:WP_Automatic_Updater::run()	Kicks off the background update process, looping through all pending updates.
wp-admin/includes/ms.php:avoid_blog_page_permalink_collision()	Avoids a collision between a site slug and a permalink slug.
wp-admin/includes/ms.php:wpmu_delete_blog()	Delete a site.
wp-admin/includes/upgrade.php:wp_upgrade()	Runs WordPress Upgrade functions.
wp-includes/class-wp-rewrite.php:WP_Rewrite::rewrite_rules()	Constructs rewrite matches and queries from permalink structure.
wp-includes/ms-functions.php:wp_schedule_update_network_counts()	Schedules update of the network-wide counts for the current network.
wp-includes/ms-functions.php:maybe_redirect_404()	Corrects 404 redirects when NOBLOGREDIRECT is defined.
wp-includes/functions.php:get_dirsize()	Get the size of a directory.
wp-includes/ms-deprecated.php:is_main_blog()	Deprecated functionality to determin if the current site is the main site.