Connected inventory: inside one store and between stores
"Connected inventory" means two different things, and apps that do one rarely do the other. Knowing which one you need saves an install and a refund request.
Inside one store
Several products or variants share the same physical stock: a bundle and its components, a gift hamper, the same item listed twice for two audiences, raw material used by three finished goods. When one sells, the others have to drop.
This is a single-store problem, solved by linking items within that store, and there are dedicated apps for it - NASP Connected Inventory is one, at $9.99 a month on its listing as of 6 August 2026. Nothing leaves the store, so no second store is involved at all.
Between two stores
The same catalogue exists in two Shopify stores - a wholesale store and a retail one, a main store and an expansion store for another market - and both have to show the same products and the same stock.
This is a different job: it needs a decision about which store owns the catalogue, a way to recognise the same product on both sides, and a way to tell whether the two are still identical a month later. That is what StoreTwin does.
How to tell which one you need
Ask where the two things that must stay in step live. Same store, different products: you need in-store linking. Different stores, same product: you need store-to-store sync.
Both at once is a real case - a bundle in the receiving store built from products that arrive by sync - and it needs both kinds of app. They do not conflict as long as only one of them writes the stock of any given product; two writers on one number is how numbers start flipping back and forth.
If it is the between-stores case
The questions worth asking any vendor: what happens when a product cannot be matched with certainty, does anything ever get deleted, and how do I see today whether the stores actually match.
StoreTwin answers those with a review queue instead of a guess, no deletion path at all, and a difference report that names the product and the field. The full boundary of what any sync app can do ยท How duplicates happen