Disable (grey out) out-of-stock swatches

If you have less variations than the AJAX variation threshold, you can grey out or disable out-of-stock attribute options. There are 2 ways to do this:

Hide out of stock products

The first option is to toggle a simple setting in WooCommerce.

1. Navigate to WooCommerce > Settings > Products > Inventory
2. Ensure "Hide out of stock items from the catalog" is checked.

   

Note: This will grey out/disable the swatch options, but it will also hide any out of stock products throughout your store.

Filter variation visibility

The second option is to add a filter to your theme's functions.php file that only affects variations.

/**
 * Disable out of stock variations
 *
 * @param bool $active
 * @param WC_Product_Variation $variation
 *
 * @return Boolean
 */
function iconic_variation_is_active( $active, $variation ) {
	if( ! $variation->is_in_stock() ) {
		return false;
	}

	return $active;
}

add_filter( 'woocommerce_variation_is_active', 'iconic_variation_is_active', 10, 2 );

This will disable swatches when a variation is out of stock, but keep out of stock products throughout the store visible (if the checkbox is the previous step is left unchecked).