Guides

Choosing a Shopify inventory sync app

Every app in this category claims real-time sync. Here are the seven questions that actually separate them, and the answers that should worry you.

Every app in this category says the same three things: real-time, reliable, easy setup. None of that separates them, and none of it is what goes wrong. What goes wrong is specific, and it is usually invisible until it has cost you an order.

These are the questions worth asking before you install anything — including this one.

1. One-way or two-way?

One-way means one store is the source of truth and the others follow it. Two-way means either store can write, which needs a rule for what happens when both change at once — and every such rule is wrong in some scenario.

Pick one-way unless each store genuinely holds its own separate physical stock. It removes the question instead of answering it. The cost is real and worth naming: edits made in the stores that follow get overwritten, so everyone has to know which admin owns the number.

2. What happens to a SKU that does not match?

This is the question that predicts the most damage, and it has three possible answers.

• Reported and skipped. The item does not sync, you get told, nothing is corrupted. This is the right answer.
• A new product is created. This is how catalogues get duplicated, and it is one of the most common complaints across every app in this category. Reasonable as a feature you asked for; a catastrophe as a default.
• Guessed at. The worst, because it is silent. If the same SKU appears twice in one store, there is no correct answer to which one the other store should follow — an app that picks will be wrong about half the time and will not tell you.

Ask specifically about the duplicate case, not just the missing case.

3. Can you watch it before it writes?

A dry run against your real catalogue, logging what it would do while touching nothing. Not a demo, not a test store — test stores have clean SKUs, which is precisely what makes them worthless for this. The whole risk lives in the messy parts of your actual data.

If a tool cannot show you its intentions before acting on them, you are trusting a stranger with the number your customers buy against.

4. What happens when you disconnect?

Ask this in writing, and read the one-star reviews for the word “deleted”. This one has its own guide, built on the nineteen reviews in our dataset that mention leaving an app — ten of which are one star.

Some apps remove products they created or reset quantities when a connection is broken. That turns an ordinary migration — the thing you will eventually do — into an incident. The safe answer is that disconnecting stops the sync and changes nothing else, in either store.

5. Is every write logged?

When a number is wrong, the first question is whether the app wrote it. Without a per-write record you cannot answer that, and you end up debugging your own business by guesswork.

A useful log says what was attempted, what happened, and why something was skipped — not just a green tick and a timestamp.

6. How is it priced?

Not three axes — eleven. We read every listing in the category on 18 September 2026 and counted what each plan actually meters, and the same shop can land on a $9 plan or a $299 one depending only on which unit the vendor chose to charge for.

Two of those are not counting your inventory at all. One — Inventory Planner — publishes no price whatsoever, so the only way to compare it is to ask.

Where the meters part company is a large catalogue. Take two stores sharing about 60,000 products, priced as of 25 September 2026: Tipo publishes no plan past 50,000 variants and Syncio none past 10,000 products, and QuickSync goes custom past 20,000 items — all three are a conversation with the vendor. Synkro is $50 per store to 100,000, so $100 for the pair; Multi-Store Sync Power is $99.99 per connected store; Easify is $59.99 for unlimited products. StockUnison is $19, because one connected store is one connected store at any catalogue size.

The rule underneath the table: per-catalogue pricing moves for reasons unrelated to how much syncing you are doing, and per-connected-store pricing moves only when you buy more of what you came for. Neither is virtuous; they just fail differently, and the one that fails badly for you depends on whether your catalogue or your store count is the thing that grows. The whole field with each meter set against its price is the page to price your own shape against.

7. Who answers when it breaks?

Inventory sync fails silently by nature — a dropped webhook, an expired token, a catalogue change that quietly stops matching. You will need to ask someone about it eventually, and the useful signal is not response-time promises but whether recent reviews mention support by name or with specifics.

What about speed?

Worth less than any of the above, and usually the only thing the marketing page talks about.

Speed matters in one narrow way: a scheduled sync’s interval is its window of wrongness, and that window gets worse exactly when you are busiest, because more sales land inside it. Event-driven sync does not degrade under load. But an event-driven sync that reads a quantity, does arithmetic, and writes it back can still lose a race against a simultaneous sale — so the question underneath “how fast” is whether the write is conditional. That detail is invisible from outside and worth asking about directly.

A shortlist you can actually run

1. Export products from both stores and count duplicate and blank SKUs. Twenty minutes, and it predicts most of how any app will behave for you.
2. Install the shortlist on the free tier and let each one match your real catalogue — every one of them in a preview or read-only mode, and never two of them writing at once, because two sync apps on the same products count each other’s writes as sales.
3. Compare what they claim matched. Disagreements between two apps on the same data are the most informative thing you will see.
4. Ask each vendor the disconnect question in writing.
5. Only then look at price.

Where StockUnison sits

One-way only. Duplicates reported and never synced. No product ever created in a connected store, nothing ever deleted. Every connection starts in preview mode, every write is logged with its result, and pricing is per live connected store — one in preview mode or paused does not count. Support reaches the person who writes the code.

It is the wrong choice if you need two-way sync, marketplace channels, or products and prices copied rather than quantities. And it is new: launched August 2026, with no review history to check, which is a real disadvantage against every established option and one you should weigh rather than take on faith. The free plan exists partly so you can run steps 1 to 3 above without trusting anything.

For the specific apps in this category and their public review records, see the comparison of Syncio and its alternatives. For pricing on this one, see the pricing page.