”One” is usually the default quantity whenever a product is added to cart. The “Add to Cart” button is often accompanied by a quantity selector that allows customers to add larger quantities of the product to their cart. Yet, shoppers might want to change the quantities of their cart items for a number of reasons:


Delete the product

Within the quantity selector drop-down on the cart page, customers should have the option of setting the quantity to zero, an action which should in turn automatically delete the product from their cart.

You can argue that customers can use the “Remove Item” link to get rid of unwanted products in their cart and many do but there is a small minority who simply like setting the quantity to zero. 

For others, it’s just a matter of convenience. Let’s take Jonah, for example. He goes into a clothing store and buys two suits, four white shirts, four neckties, and two pairs of wingtips. When he’s about to check out, realizes that the total is higher than his budget. He already has a fairly decent pair of wingtips so he adjusts the quantity from two to one but the running total is still a little above his budget. At this point, setting the quantity of wingtips to zero pairs is a lot easier for Jonah than finding the “Remove item” link.


Auto-Update cart

Auto-update the cart as soon as it’s changed. See best practice #207 about the cart being auto-updated with any quantity changed.