What does "frequently bought together" mean?

Where the pairings come from

The useful version of this block is built from your own order data. It looks at which products appear in the same basket often enough that the pattern is unlikely to be coincidence, then ranks those pairings by how reliably they repeat. That is why it finds combinations nobody would tag by hand: a specific sock with a specific boot, or a refill with the one size of container it fits.

The weaker version is manual. Someone picks three related products per item and the list ages the moment the catalog changes. It works on a small range and quietly stops reflecting reality as the catalog grows.

Why it is not the same as related products

Related products are similar to the item being viewed: another shirt, another shade. Frequently bought together is complementary: the thing you also need. Showing similar items to someone who has already chosen invites them to reconsider rather than to add, which is why the two blocks belong in different places.

What makes it work or fail

Stock is the usual failure. A pairing that recommends something unavailable wastes the slot and sends the shopper to search for it elsewhere. The same applies to margin: a block that reliably promotes your thinnest-margin accessory is raising order value while lowering what you keep.

Placement matters too. On the product page the shopper has chosen, so complements land well. In the cart they have committed, so small additions land well. On a collection page they are still deciding, and a complement there is premature.

Setting it up on Shopify

Shopify does not generate this natively from order history, so it comes from an app. What separates them is what the recommendation is allowed to consider: purchase affinity alone, or affinity balanced against current stock, margin and the shopper's own behavior. Kimonix uses the same signals that drive collection ordering, so a recommendation obeys the same rules as the rest of the storefront.