Inventory that agrees with itself.
Keep stock in perfect sync across all your Shopify stores — B2C, B2B, regional, multi-location — so the oversells, wipes, and duplicate catalogs from other sync apps can't happen to you.
Read-only to start · every write logged · nothing ever deleted
Install on Shopify Free plan, forever · live syncing from $19/mo · founder-run supportLive demo
Click through it — it's interactive, not a video.
Retail → B2B Dry run
Try the sync
Then change stock on the Products tab and watch what the current mode does — in the Activity log and the Drift report.
Change stock on Retail below. A matched SKU is copied to B2B — instantly in Live mode, or held back (shown in red) in Dry-run and Paused.
Run matching first (Matches tab) so changes can sync.
| Product | SKU | Retail | B2B |
|---|
SKU matcher
Pairs variants by SKU and flags duplicates — which are never synced. Matching is about which SKUs line up between stores, not their quantities; quantity differences show on the Drift page.
No matches yet — run matching to build the report.
| SKU | Status |
|---|
→ Next: Matching is a one-time setup — this report only changes when your catalog does, not when you edit stock. To watch a sync happen, open Products, change a quantity, then check Activity and Drift.
Check drift
Compares "available" inventory on both stores for every matched SKU and flags any difference.
Result
Every sync decision — real or dry-run — is written here. Both stores read the same log; nothing happens silently.
| Time | SKU | Change | Result |
|---|
No sync activity yet. Change stock on the Products tab to see events here.
The idea
One quantity. Two stores. Always the same number.
A sale on one store, a restock on the other — and the count on both never disagrees, never goes negative.
The failure stories
If you run multiple stores, you know these stories
The three most repeated disasters across every multi-store sync app's one-star reviews:
A stock update races a sale, quantities go to −2, and you're emailing customers about orders you can't fill.
One ambiguous SKU match, and your catalog becomes a cleanup project measured in days.
Everything looks green until a customer orders something that sold out on the other store yesterday.
Paraphrased from public Shopify App Store reviews of leading sync apps, 2019–2026.
The guarantees
The three guarantees StockUnison is built on
Not features — invariants. Each one exists because a category of one-star review has to become impossible.
Atomic updates
A restock can never race a sale into negative inventory. Every quantity change lands whole, or not at all.
No silent drift
Every sync run is logged and verifiable. A drift report shows any mismatch — you see problems before your customers do.
Never destructive
No duplicate creation — and it never deletes anything, period. New connections start in dry-run, and disconnecting leaves both stores intact.
The mechanism
One source, every store — one-way
You pick one store as the source; every other store follows it. Each change travels a single guarded path from the source out to each destination below — never the other way, and never between destinations.
How it works
Three steps from two disagreeing catalogs to one verifiable truth
Connect your stores
Pair two stores with a one-time code. StockUnison maps SKUs and shows you exactly what matches — and what doesn't — before anything syncs.
Watch the dry run
Every would-be change appears in the activity log while nothing is written. Duplicate SKUs are never synced — ever. Flip to live when the plan matches reality.
Stay in unison
Real-time atomic sync from then on, with a live log and drift report proving your stores agree.
The proof
Printed proof of every write
Real or dry-run, every decision the sync makes is written to a log both stores can read. Nothing happens silently.
- 09:41:07HAT-00111 → 30APPLIED
- 09:41:07HAT-00130 → 29APPLIED
- restock met a live sale — serialized, landed wholeATOMIC
- 09:44:12MUG-10452 → 51APPLIED
- 09:47:58TEE-009duplicate SKUSKIPPED
- never synced — nothing deleted
- 09:52:33BAG-2017 → 6APPLIED
- 09:55:00DRIFT12/12 SKUs agreeVERIFIED
- entries 6applied 4skipped 1lost 0nothing deleted · nothing silent
Built by the person who answers your email
A note from the founder. I'm an independent developer. Before writing a line of StockUnison I read 2,603 reviews of every multi-store sync app on the Shopify App Store — including 163 detailed one-, two- and three-star stories of overselling, duplicated catalogs and wiped inventory.
StockUnison is the answer to those specific failures — and it's on the App Store now, syncing real stores with every decision logged and verifiable. There's a free plan you can stay on, and you'll be talking directly to the person who writes the code.
Questions you should ask a brand-new app
When can I actually use it?
Now — StockUnison is live on the Shopify App Store. Install it free on the store whose stock everyone should follow, connect a second store with the code it gives you, and you're syncing. Setup takes a few minutes and needs no call, no demo and no card; the setup guide walks every step. Support still comes from the person who writes the code.
How big can my catalogue be?
Up to 10,000 product variants per store today. That covers the overwhelming majority of multi-store merchants; if you're above it, write to me before installing and I'll tell you honestly where the work stands.
What does it cost?
There is a Free plan you can stay on: unlimited SKU matching, unlimited dry run, the full activity log and drift detection — everything except writing to a destination store. Live syncing is $19/month for one destination store (Starter), $39/month for up to five (Growth), and $79/month for unlimited (Scale). Every paid plan has a 14-day free trial, and only the source store pays — destinations always install free. Flat and public: no per-store creep, no feature ransoms, and billing runs through your Shopify invoice, so there is no card to enter.
What exactly does it sync?
Shopify to Shopify only, by design: inventory today, with products and prices next on the roadmap under the same guarantees. No marketplaces, no POS feeds — depth over breadth. If you're still weighing approaches, the guide on syncing inventory between two Shopify stores covers CSV and custom builds too.
Why trust a new app with inventory?
Because it's built assuming you shouldn't. Connections start read-only, every write is previewed and logged, nothing is ever deleted without confirmation, and the drift report lets you verify — not trust — that your stores agree. There's also an honest comparison against the established apps, including where this one is the weaker choice.
Two stores. One truth.
Install free and connect your second store in a few minutes. Every connection starts in dry run, so you see exactly what would change before anything moves — and there's a founder on the other end of every email.
Install on ShopifyQuestions first? Read the setup guide or write to [email protected]