WordPress at a glance
filter is not described

admin_body_class filter-hook . WP 1.0

This filter is documented in wp-admin/admin-header.php

Usage

add_filter( 'admin_body_class', 'filter_function_name_8461' );
function filter_function_name_8461( $string ){
	// filter...

	return $string;
}
$string
-

Where the hook is called

iframe_header()
admin_body_class
wp-admin/includes/template.php 2075
$admin_body_classes = apply_filters( 'admin_body_class', '' );
wp-admin/admin-header.php 227
$admin_body_classes = apply_filters( 'admin_body_class', '' );

Where in WP core the hook is used WordPress

wp-admin/includes/class-wp-site-health.php 49
add_filter( 'admin_body_class', array( $this, 'admin_body_class' ) );
wp-admin/nav-menus.php 580
add_filter( 'admin_body_class', 'wp_nav_menu_max_depth' );
wp-admin/widgets.php 32
add_filter( 'admin_body_class', 'wp_widgets_access_body_class' );