Shopify cart not working: why items vanish

Many stores answer to more than one address: the plain domain, the version with www, or an older domain that still redirects. A browser saves cookies per address, and the cart is kept in one of them. A shopper who starts at the ad's address and then follows a link to the other address begins with an empty cart, while the item sits saved on the first one. Nothing on the screen says so. The shopper sees the header count drop to zero or the cart page open empty, and they assume the store lost the item.

• Add an item from the plain address, then open the www address. Is the item still in the cart?
• Note the count in the header, then open the cart page. Do the two show the same number?
• Add an item, then open the cart in a private window. Does the item appear?
• Follow an ad link and a menu link to the store. Do both addresses show the same cart?
• Remove an item on the cart page, then check the header count. Does it update at once?

A shopper rarely types the store's address themselves. They arrive from an ad, a search result, a social post or a bookmark, and each one can use a different version of the address. The first visit saves the cart in a cookie for that version. The next visit, to the other version, reads a different cookie and finds nothing there. If the store then sends the shopper across to its main address, the redirect carries the page but not the old cart, so the shopper starts over. The owner rarely sees this, because the owner's own bookmark always uses the same version of the address, and that version keeps one cart.

A store can show the cart in several places: a count in the header, a cart drawer or page, and a total near the checkout button. Each one can be drawn from a separately loaded copy of the cart. The header count is the easiest to check. When the count rises after an add but the cart page is empty, the page read a different cart, which usually means a different address. When the count stays at zero but the page lists the item, the header read a stale copy. Note the address in the bar each time a number changed. An address that changed between the add and the cart page is the first thing to check.

The check is to add an item from every address that serves the store, then open the cart from a link on the page, not from the browser's history. Run it on a phone as well as a laptop, since each browser keeps its own saved cart. A simulated test does the same. It arrives through the addresses you point it at, adds an item, and reads the count and the cart page at each one.

The report gives the step and a screenshot for each address, so you can see which one lost the item. Compare the screenshots from the add and from the cart page, since the address in the bar on each one is the clue. It does not say how many shoppers come in on each version, so use your analytics to decide which address to fix first.

A new domain, a changed www setting, a preview address or a redirect rule can start a second cart for everyone who arrives on the other address. After any domain or redirect change, add an item from each address that serves the store, and open the cart from a link on the page. Run the same check on each preview address your team shares, since a shopper may land there from a review link.