WP_MS_Sites_List_Table::get_columns

		$sites_columns = array(
			'cb'          => '<input type="checkbox" />',
			'blogname'    => __( 'URL' ),
			'lastupdated' => __( 'Last Updated' ),
			'registered'  => _x( 'Registered', 'site' ),
			'users'       => __( 'Users' ),
		);

		if ( has_filter( 'wpmublogsaction' ) ) {
			$sites_columns['plugins'] = __( 'Actions' );
		}

		/**
		 * Filters the displayed site columns in Sites list table.
		 *
		 * @since MU (3.0.0)
		 *
		 * @param string[] $sites_columns An array of displayed site columns. Default 'cb',
		 *                               'blogname', 'lastupdated', 'registered', 'users'.
		 */
		return apply_filters( 'wpmu_blogs_columns', $sites_columns );
	}