WordPress at a glance
filter is not described

old_slug_redirect_url filter-hook . WP 4.4.0

Filters the old slug redirect URL.

Usage

add_filter( 'old_slug_redirect_url', 'filter_function_name_9865' );
function filter_function_name_9865( $link ){
	// filter...

	return $link;
}
$link(string)
The redirect URL.

Where the hook is called

wp_old_slug_redirect()
old_slug_redirect_url
wp-includes/query.php 1006
$link = apply_filters( 'old_slug_redirect_url', $link );

Where the hook is used (in WP core)

Does not used.