WordPress at a glance
filter is not described

get_site_icon_url filter-hook . WP 4.4.0

Filters the site icon URL.

Usage

add_filter( 'get_site_icon_url', 'filter_function_name_1536', 10, 3 );
function filter_function_name_1536( $url, $size, $blog_id ){
	// filter...

	return $url;
}
$url(string)
Site icon URL.
$size(int)
Size of the site icon.
$blog_id(int)
ID of the blog to get the site icon for.

Where the hook is called

get_site_icon_url()
wp-includes/general-template.php 805
return apply_filters( 'get_site_icon_url', $url, $size, $blog_id );

Where the hook is used (in WP core)

Does not used.