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filter is not described

wp_nav_menu filter-hook . WP 3.0.0

Filters the HTML content for navigation menus.

Usage

add_filter( 'wp_nav_menu', 'filter_function_name_1558', 10, 2 );
function filter_function_name_1558( $nav_menu, $args ){
	// filter...

	return $nav_menu;
}
$nav_menu(string)
The HTML content for the navigation menu.
$args(stdClass)
An object containing wp_nav_menu() arguments.

Where the hook is called

wp_nav_menu()
wp-includes/nav-menu-template.php 253
$nav_menu = apply_filters( 'wp_nav_menu', $nav_menu, $args );

Where the hook is used (in WP core)

wp-includes/class-wp-customize-nav-menus.php 1179
add_filter( 'wp_nav_menu', array( $this, 'filter_wp_nav_menu' ), 10, 2 );