Back-in-stock apps for Shopify all list the same headline features, so the listing pages look interchangeable. The things that actually separate them are which notification channels they send on and what each message costs, how the app decides who to alert when a restock is smaller than the waitlist, whether multi-language covers every channel or only email, and whether the free plan lets you find out if restock demand exists in your catalogue at all. This covers those, with the verified numbers for the listings we could read.
The listings we could verify
Read from the live App Store listings on 12 September 2026. These are the apps whose pages we could retrieve and check — not a ranked shortlist, and not the whole category.
| App | Rating | Reviews | Built for Shopify | Published pricing |
|---|---|---|---|---|
| Amp Back in Stock & Preorder | 4.9 | 941 | Yes | Free / $19 / $49 / $99 |
| Notify‑me — Stock and Price | — | — | Yes | Free / $9.90 / $24.90 / $49.90 |
| Stok (ours) | 4.8 | 118 | Yes | Free / $10 / $20 / $49.99 |
The number that matters most there is not ours. Amp has 941 reviews at 4.9; Stok has 118. That is an eight-fold difference in evidence, and a merchant choosing on track record should weigh it accordingly. We are not going to pretend otherwise in an article we wrote.
Swym, Appikon and Restock Rocket are also in this category and are frequently recommended. We could not retrieve their listings to verify current figures, so they are named here without numbers rather than described from memory.
1. Which channels, and what does each message cost?
The biggest functional difference in the category, and the one with an ongoing bill attached.
- Email is universal and effectively free to send. Every app has it. It is also the slowest to be seen, which matters because a limited restock can be gone within the hour.
- SMS is opened within minutes and costs a few cents a message. Common but not universal.
- WhatsApp is the one most apps skip, and it decides the outcome in India, Brazil, Indonesia, the UAE and much of southern Europe, where a marketing email is close to invisible.
If a meaningful share of your customers are in a WhatsApp-first market, that single fact should probably decide the choice, because it eliminates most of the category.
Check the per-message cost, not the monthly fee. At volume that is where the real bill comes from — including the cost of an email above your plan's allowance, which several apps charge for and few advertise.
2. How does it decide who to notify?
The question almost nobody asks before installing, and the one that produces the worst outcome when the answer is wrong.
Four hundred people are waiting. You restock thirty. An app that notifies everyone has just produced three hundred and seventy customers who clicked through to a sold-out page for the second time, and who now know your restock emails are not worth opening.
What to look for:
- Quantity-matched notification — alert only as many subscribers as you have units, in the order they joined.
- Batched sending — notify in waves and stop when stock runs out.
If an app only offers "notify all", it will create that problem for you eventually. This is not a luxury feature. More on why it matters.
3. Does multi-language cover every channel?
Email-only translation is common and half useful.
Two questions: does the notification go out in the language the customer was browsing in, automatically, or does it need a template maintained per language by hand? And does that apply to SMS and WhatsApp as well as email?
The second catches people. An app advertising "30 languages" may mean thirty email templates and one SMS string.
4. Preorders: included, or a separate product?
Alerts and preorders answer the same situation differently — "we will tell you when it is back" versus "pay now, ships later" — and most catalogues want both, chosen per product.
Some apps bundle preorders; others sell them as a separate subscription. If you expect to use both, count that cost in when comparing monthly prices, because it can double the real figure.
Also check the preorder limit. Several apps cap preorder offers or preorder orders per month on lower tiers, which is a limit you will hit exactly when a preorder is working.
5. What can the free plan actually tell you?
You cannot know whether restock demand exists in your catalogue until you have collected signups for a month. An app that requires payment before you can measure that is asking you to guess.
What to check: does the free plan allow unlimited subscriber collection, even if it limits how many notifications you can send? Collection is the measurement. Sending is the conversion, and it can wait a month.
A free plan capping signups tells you nothing about demand. One capping sends tells you everything you need to decide.
What the pricing actually scales on
Every app in this category prices on something different, which makes the headline monthly figures close to meaningless until you map them to your own numbers.
The three models:
- By notifications sent. Costs track how often you restock. A store with frequent small restocks pays more than one with rare large ones, even at identical revenue.
- By subscribers collected. Costs track how much out-of-stock traffic you have — which is the thing you are trying to grow, so this model charges you more as the programme works.
- By feature tier. A flat fee with channels and languages gated. Predictable, and you pay for the tier even in a month with no stockouts.
Work out your own number before looking at any pricing page: how many out-of-stock products do you have in a typical month, and roughly how many people would join a waitlist for each? Even a rough figure tells you which model suits you, and it is the same figure that tells you whether the programme is worth running at all.
Watch for the overage rate specifically. A plan including 100 notifications at $10 with $0.05 per additional is a different product from a flat $19 — better at low volume, worse at high — and the crossover is usually not where you would guess.
What matters less than the listings suggest
- Widget design options. It is a button and a form. Matching your theme matters; twelve layout variants do not.
- Integration count. One integration matters — your email platform, and specifically whether subscribers sync with the product they are waiting on attached rather than as a flat list of addresses.
- Template libraries. You will use one email template and edit it.
- Analytics dashboards. The number that answers "is this worth running" is recovered revenue, and most dashboards lead with signups.
A short evaluation
- List the markets your customers are in. If any are WhatsApp-first, filter on that first.
- Install on a free plan and check subscriber collection is unlimited.
- Add the widget to a sold-out product and a collection page — half your signups come from the grid.
- Ask support directly what happens when the waitlist exceeds the restock.
- Send a test notification in a second language, on SMS or WhatsApp if you use them.
- After a month, look at signups per product. That is your demand data, and it is worth having whichever app you keep.
Where to go next
Before comparing apps it is worth settling how you will use them — channel choice, send timing, and whether a preorder beats an alert for a given product. That is covered in the back-in-stock guide, and the preorder decision specifically in preorders or alerts.
Stok sends on email, SMS and WhatsApp from the $10 plan, handles 29 languages across all three, and collects unlimited subscribers on the free plan.
