A stockout does not announce itself. One day a product is selling normally, and the next it is sitting at zero units while the listing is still live, still running ads, and still collecting orders your team has to cancel by hand. By the time someone notices, the damage is already showing up as cancelled orders, refunds, and a listing that ranks lower because it could not fulfill demand.
Inventory distortion, the combined cost of stockouts and overstocks, is on track to cost global retail roughly $1.7 trillion in 2026, or 6.2% of worldwide retail sales, and out-of-stocks account for almost two-thirds of that figure. Low-stock alerts are the cheapest fix available for that problem. They do not require a warehouse management system or a six-figure budget, just a threshold, a notification, and someone who acts on it before the count hits zero. This guide walks through exactly how to set up low-stock alerts and low-stock notifications in both Shopify and WooCommerce, the platforms behind most of Avezant’s e-commerce clients.
What Low-Stock Alerts Actually Do
A low-stock alert is a rule: when a product’s available quantity drops to a number you choose, the system sends a notification, usually by email, before the product reaches zero. The mechanism is simple, but the value is in the timing. An alert set at “0 units left” only tells you what a customer already found out. An alert set at a meaningful buffer, for example 10 units on a SKU that sells 15 a week, gives your team enough runway to reorder, pause ads, or adjust a listing before the product actually goes unavailable.
The threshold is the entire strategy. Set it too low and the alert fires at the same moment you are already out of stock. Set it too high on a slow-moving SKU and you get alert fatigue, emails your team starts ignoring. The right inventory threshold is tied to how fast each product actually sells, not a single number applied to the whole catalog.
How to Set Up Low-Stock Alerts in Shopify
Shopify’s native automation tool, Shopify Flow, is built to handle low-stock notifications without installing a separate app.
- Turn on inventory tracking for the product in Shopify admin (Inventory tab, “Track quantity”), since Flow can only watch stock levels that Shopify is actually tracking.
- Open Shopify Flow from the Shopify admin apps menu and start a new workflow, or install the “Get notified when product inventory is low” template directly.
- Set the trigger to “Inventory quantity changed,” which fires every time a sale, return, or manual edit changes a variant’s stock count.
- Add two conditions: “Product variant inventory quantity” equal to your threshold (for example, 5), and “Product variant inventory quantity prior” greater than that threshold. This combination fires the alert only the moment stock first crosses the line, not every time it changes afterward.
- Add the “Send internal email” action and set the recipient to whoever owns reordering, so the alert reaches an inbox someone actually checks.
- Turn the workflow on and test it by editing a test product’s quantity down to the threshold to confirm the email arrives.
Stores that want something lighter than building a Flow from scratch can also use a dedicated low-stock alert app from the Shopify App Store, most of which add per-SKU thresholds and daily digest emails on top of the same underlying inventory data.
How to Set Up Low-Stock Alerts in WooCommerce
WooCommerce builds low-stock notifications into the core plugin, no extra install required, inside WooCommerce’s product settings.
- Go to WooCommerce > Settings > Products > Inventory in the WordPress admin.
- Check “Enable stock management” if it is not already on, since every alert depends on WooCommerce tracking real quantities.
- Set the “Low stock threshold” to the quantity that should trigger a warning across your catalog, for example 5 units.
- Set the “Out of stock threshold” separately, the point where the product actually switches to an out-of-stock status on the storefront.
- Enter one or more addresses in “Notification recipient(s),” separated by commas, so alerts reach everyone who needs to reorder, not just the site admin.
- Tick “Enable low stock notifications” and “Enable out of stock notifications.” Both boxes need to be checked, and the recipient field needs to be filled in, or nothing sends.
- Override the threshold per product when needed by opening that product’s edit screen, going to the Inventory tab, and setting its own “Low stock threshold.” This overrides the global number for fast- or slow-moving SKUs that do not fit a one-size-fits-all rule.
Why Programming These Alerts Pays Off
| Benefit | What it does | Why it matters |
|---|---|---|
| Catches the problem early | Flags a product days or weeks before it actually hits zero | Leaves enough time to reorder or adjust instead of reacting after the sale is already lost |
| Protects ad spend | Signals when a promoted product needs to be paused or its budget reduced | Stops paying to drive traffic to a listing that is about to be unavailable |
| Reduces cancelled orders | Gives staff a window to pause selling before a product oversells to zero | Fewer cancellations means fewer refunds and less damage to marketplace account health |
| Improves reorder timing | Ties restocking to actual sell-through instead of a fixed calendar check | Keeps cash tied up in the right inventory instead of the wrong one |
| Removes manual stock checks | Replaces someone eyeballing a spreadsheet or dashboard daily | Frees up time for merchandising, ads, and customer service |
| Preserves customer trust | Keeps “in stock” on the storefront accurate to what can actually ship | Fewer broken promises means fewer one-time buyers who never return |
Mistakes That Make Alerts Useless
The most common failure is not the absence of an alert. It is a threshold nobody ever revisits. A number set once at launch stops matching reality as a product’s sell-through rate changes with seasonality, promotions, or new channels added later. The second most common mistake is sending alerts to an inbox nobody checks, usually a generic admin address instead of whoever actually places reorders. The third is treating every SKU the same: a product that sells 2 units a week and one that sells 50 units a week need very different thresholds, and a single global number will always be wrong for one of them.
A low-stock alert only works if the threshold reflects how fast a product actually sells and the notification reaches someone who can act on it the same day.
How Avezant Turns Alerts Into a Full System
Avezant’s ecommerce automation work starts with getting thresholds right per SKU, then connects the alert itself to a reorder workflow, so a low-stock notification does not just sit in an inbox waiting for someone to act on it manually.
For stores selling across more than one platform, alerts have to account for combined stock across every channel, not just one. That is the core of Avezant’s multichannel expansion work, keeping a single accurate count that every channel reads from before a threshold is ever set.
If your store is still checking stock manually or getting alerts nobody acts on, start with a free ecommerce audit. Avezant will review your current setup and show you exactly where inventory visibility is breaking down before it costs another sale.
Sources: Shopify Help Center: Shopify Flow workflow examples, WooCommerce: Products Settings Documentation, Retail Insight Network: How overstock, stockouts, and returns cost retail $1.75tn.