WordPress at a glance
filter is not described

exit_on_http_head filter-hook . WP 3.5.0

Filters whether to allow 'HEAD' requests to generate content.

Provides a significant performance bump by exiting before the page content loads for 'HEAD' requests. See #14348.

Usage

add_filter( 'exit_on_http_head', 'filter_function_name_2779' );
function filter_function_name_2779( $exit ){
	// filter...

	return $exit;
}
$exit(true/false)
Whether to exit without generating any content for 'HEAD' requests.
Default: true

Where the hook is called

In file: /wp-includes/template-loader.php
exit_on_http_head
wp-includes/template-loader.php 24
if ( 'HEAD' === $_SERVER['REQUEST_METHOD'] && apply_filters( 'exit_on_http_head', true ) )

Where the hook is used (in WP core)

Does not used.