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Out of stock notifications on Shopify
This phrase covers two completely different jobs and the apps that do them do not overlap. Work out which one you need first, because installing the wrong category is a common and avoidable mistake.
Last reviewed 16 August 2026
Two different jobs
- Telling customers when something is back. A back in stock notification, captured on the product page and sent to a shopper. Recovers a sale you already lost.
- Telling your team that stock hit zero, or better, that it is about to. Prevents the loss instead of recovering it.
This page is about the second. Both are worth having, in that order of priority, because prevention is cheaper than recovery.
On this page
Why an out of stock alert already arrives too late
By the time stock reaches zero the damage is done. The product page is already unbuyable, ads may still be spending against it and customers are already meeting the sold out state.
An out of stock alert is still worth having, because unnoticed zeros run for weeks. But it should be the backstop, not the main line of defence. The alert that saves money fires while stock is still positive and there is time to do something.
Practically that means running both: a low stock alert at a lead time based threshold as the primary warning, plus an out of stock alert as the safety net for anything that slipped through.
Setting up the internal alert
With Shopify Flow, free on paid plans:
- Create a workflow on the inventory quantity changed trigger.
-
Add a condition on
productVariant/inventoryQuantityequal to 0 for the out of stock case, or less than or equal to your threshold for the earlier warning. - Send an internal email to the people who can act on it.
With an alerts app: both conditions are usually settings rather than separate builds and the alert is evaluated per location.
Watch the continue selling setting. A variant set to continue selling when out of stock goes negative rather than stopping at zero. If your condition tests for exactly 0 it can miss entirely. Test for less than or equal to 0 instead.
Available is not the same as on hand
Shopify tracks several quantities and picking the wrong one produces alerts that feel wrong.
- Available is what a customer can buy. This is almost always the number your alert should use.
- Committed is allocated to orders not yet fulfilled.
- On hand is physically present, including committed units.
A product can have healthy on hand stock and zero available because it is all committed to unfulfilled orders. Alerting on on hand hides that case completely, which is exactly the case you needed to know about.
Also tell the customer
Once your team is covered, a back in stock notification on the product page recovers demand you would otherwise lose. It is a different category of app and worth having, but it is second in priority: it recovers a sale you already missed, while the internal alert stops you missing it.
Catch it before zero
Stockwell alerts on low stock and on out of stock, per location, so the early warning and the backstop are both covered without building a workflow for each.
Get Stockwell on the Shopify App Store Free plan covers 50 SKUs with a daily summary. Paid plans add instant alerts and more recipients. No card needed to start.Common questions
How do I get notified when a product is out of stock on Shopify?
Build a Shopify Flow workflow on the inventory quantity changed trigger with a condition testing for zero or below, or use an alerts app. Shopify does not send this notification on its own.
What is the difference between a back in stock alert and an out of stock alert?
A back in stock alert goes to a customer who asked to be told when an item returns. An out of stock alert goes to your team to tell them something needs restocking. Different apps, different purpose.
Should I alert at zero or before?
Before. At zero the sale is already lost. Use a lead time based low stock threshold as the primary alert and keep the zero alert as a backstop for anything that slipped past.