WordPress at a glance
filter is not described

woocommerce_thankyou_order_key filter-hook . WC 1.0

Get the order.

Usage

add_filter( 'woocommerce_thankyou_order_key', 'filter_function_name_1648' );
function filter_function_name_1648( $empty ){
	// filter...

	return $empty;
}
$empty
-

Where the hook is called

WC_Shortcode_Checkout::order_received()
woocommerce_thankyou_order_key
woocommerce/includes/shortcodes/class-wc-shortcode-checkout.php 234
$order_key = apply_filters( 'woocommerce_thankyou_order_key', empty( $_GET['key'] ) ? '' : wc_clean( wp_unslash( $_GET['key'] ) ) ); // WPCS: input var ok, CSRF ok.

Where in WP core the hook is used WooCommerce

Usage not found.