Promo codes are usually intended for specific products or categories, but their use can vary depending on the code and the item you want to buy. Sometimes, promo codes can be used for pre-orders or already discounted items, but other times they might not be accepted for these purchases.
To avoid any confusion, it's a good idea to check the terms and conditions of your promo code before you go to checkout. This way, you'll know exactly what the restrictions and eligibility rules are, helping you get the best out of your discount.