WordPress at a glance
filter is not described

(field)_pre filter-hook . WP 2.3.0

Filters the value of a specific post field before saving.

The dynamic portion of the hook name, $field, refers to the post field name.

Usage

add_filter( '(field)_pre', 'filter_function_name_2322' );
function filter_function_name_2322( $value ){
	// filter...

	return $value;
}
$value(mixed)
Value of the post field.

Where the hook is called

sanitize_post_field()
(field)_pre
wp-includes/post.php 2233
$value = apply_filters( "{$field}_pre", $value );

Where the hook is used (in WP core)

wp-includes/default-filters.php 250
add_filter( 'title_save_pre', 'trim' );
wp-includes/kses.php 1704
add_filter('title_save_pre', 'wp_filter_kses');
wp-includes/kses.php 1713
add_filter('content_save_pre', 'wp_filter_post_kses');
wp-includes/kses.php 1714
add_filter('excerpt_save_pre', 'wp_filter_post_kses');
wp-includes/kses.php 1715
add_filter('content_filtered_save_pre', 'wp_filter_post_kses');
wp-includes/kses.php 1732
remove_filter('title_save_pre', 'wp_filter_kses');
wp-includes/kses.php 1739
remove_filter('content_save_pre', 'wp_filter_post_kses');
wp-includes/kses.php 1740
remove_filter('excerpt_save_pre', 'wp_filter_post_kses');
wp-includes/kses.php 1741
remove_filter('content_filtered_save_pre', 'wp_filter_post_kses');