We've spent months running Shopify stores and working alongside merchants who do. Couple months ago, one of those stores sold out of its best product two weeks before the holidays and their subscriptions with Subi Froze too. We watched the analytics tell us, in real time, exactly how much that hurt. Hundreds of product page visits, zero ways to capture any of them.
So we went looking for a restock app. And because we're the kind of team that has one of the best in-class subscription and loyalty apps, we ended up installing eight of them on a clone of the store and running them in parallel for six weeks.
This article is the result. We're going to tell you which ones we'd actually keep, which ones we uninstalled in under a day, and the things nobody mentions in the polished App Store screenshots.
The Built for Shopify badge mattered too, but mostly because the badged apps consistently loaded faster on product pages. In a store where you obsess over Core Web Vitals, that's not nothing.
Rating: 4.9★ (3100+ reviews) · Built for Shopify · Free plan available
This is one of the ones we kept installed.
The reason is boring and practical. We were already planning to install a wishlist app and were thinking about offering preorder for one of our products. Notify Me! does all three jobs from one dashboard, with one set of branded notifications. Consolidating from "three apps we half-understand" to "one app we actually know" was worth more to us than any individual feature.
A few things stood out during testing:
What we didn't love: the dashboard has a lot going on. The first 2 minutes felt overwhelming because the app is doing three jobs at once. Once we'd configured each piece and stopped touching the settings, this stopped mattering. The onboarding flow could still be tighter.
Rating: 5.0★ (3,200+ reviews) · Built for Shopify · Free plan available
The most-reviewed app in this category by a wide margin, and after testing it we understand why. The free tier is genuinely usable, the email delivery is fast, and setup took about six minutes.
If all you need is restock alerts and you don't want to think about preorder or wishlist, this is a good choice. The reason it's not at the top of our list is that we personally needed more. If we were running a single-SKU store or a tightly focused catalog, we'd happily install Kbite and call it done.
What we noticed: the email templates are functional but plain. If your brand has any visual identity, plan to spend 30 minutes customizing.
Rating: 4.8★ · Built for Shopify · Free plan available
AMP has been around forever. We saw merchant reviews from stores that have been on it for 8+ years, which says something about both the product and the team behind it.
The interface is more complex than Kbite or Stoq, and during our test we had a moment of "wait, where is that setting" twice. But the feature depth is real, and if we were running a 5,000-SKU catalog or a B2B store with complex variant logic, we'd take Swym's complexity over a simpler app's limitations.
What we noticed: this is not the app for a solo founder running 30 SKUs. It's overkill, and overkill is its own kind of friction.
Rating: 5.0★ (720+ reviews) · Built for Shopify · Free
Fully free. No tier game, no "starter plan that's actually a trial." That's rare.
REZ does both restock alerts and preorder, has the Built for Shopify badge, and was one of the easier apps to install during our test, under five minutes. Feature depth is lighter than Kbite or Notify Me!, and SMS support is limited compared to paid alternatives.
Who it's for: if you're bootstrapping and a $0 line item matters, install REZ. You can always migrate later when revenue justifies a paid tool, but they may keep your leads hostage when they introduce a paid plan (90% of the time, happens every time)
Rating: 4.7★ · Built for Shopify · Free plan available
The reason Stok shows up on our list at all is WhatsApp (combined with Notify Me!). Most apps in this category treat WhatsApp as an afterthought or skip it entirely. Stok treats it as a first-class channel alongside email and SMS.
We're based in Canada and we have customers from around the world. We know how huge WhatsApp is there, so during testing we leaned mostly on the email and SMS flows. The WhatsApp setup was clean, and the channel matters enormously in markets like India, Brazil, and most of Europe.
It also handles price drop alerts, which is adjacent but distinct, and useful if you run sales.
Rating: 4.3★ · Free plan available
Sometimes you don't want a Swiss Army knife. You want a single sharp blade. Alert Me! does one job (restock alerts, variant-aware) and gets out of the way.
We respect this app for what it is. During our test it was the fastest setup of all eight, the email delivery was reliable, and the dashboard is so simple there's almost nothing to learn.
What's missing: no preorder, no wishlist, no SMS in the free tier. If your email platform (Klaviyo, Omnisend) is doing the heavy lifting downstream, that's fine. If you wanted multi-channel from your restock app, look elsewhere.
Rating: 4.8★ · Free plan available
Appikon's distinctive move is web push notifications as a real channel. Useful for the segment of customers who won't share email or phone but will accept browser push.
We were skeptical of push as a restock channel going in. After testing, we're somewhere between cautious and convinced. Push has higher delivery rates than email, but the click-through pattern is different and you have less space for context. It's a complement to email, not a replacement.
The app itself worked fine. Setup was straightforward, the dashboard was clear, and the templates were customizable.
Rating: YTU (You Tell Us)★ · Free plan for the best comments!
Let us know which app to test next!
After days of testing, here's the framework we'd use if we were starting from zero:
If you only need restock alerts and you're cost-conscious → Kbite or Alert Me!. Both are reliable and the free tiers are real.
If you need restock plus preorder → Notify Me! or REZ. Notify Me! has more depth; REZ is fully free.
If you need restock plus preorder plus wishlist, or you're already paying for a wishlist app separately → Notify Me! or Swym. Notify Me! is friendlier for SMBs; Swym is built for larger catalogs.
If WhatsApp is a real channel for your customers → Stok.
If you're mobile-first and email open rates have been sliding → Appikon for push as a complement.
The mistake we see merchants make is picking the app with the most reviews and assuming that's the right answer. Review count is a proxy for popularity, not for fit. The right app for a 30-SKU candle store is not the same as the right app for a 5,000-SKU apparel brand, and both might have 5-star ratings.
Does Shopify have a built-in restock notification feature? No. Shopify does not natively send back-in-stock alerts. You need a third-party app from the Shopify App Store.
How much should I expect to pay? Most apps offer a free tier covering basic email alerts and a small subscriber count. Paid plans typically run $10 to $50/month for SMBs, with enterprise tiers higher based on send volume and SKU count.
Will a restock app slow down my store? A well-built one shouldn't measurably impact page speed. Apps with the Built for Shopify badge meet a higher performance bar, including asynchronous loading so widgets don't block your page render. We'd test Core Web Vitals before and after install regardless.
Email vs SMS vs push: which converts best? SMS open rates are dramatically higher than email (90%+ vs 20–25% on a good day), but cost per send is higher and customers are pickier about giving out their number. The setups that worked best for us used email as the default with SMS as an optional upgrade for high-intent subscribers.
Can I use a restock app alongside Klaviyo? Most quality apps integrate natively with Klaviyo. Confirm the integration is native rather than Zapier-based. The latter introduces lag that can matter when you've just restocked and customers are refreshing the page.
Are these apps compatible with Shopify 2.0 themes? All of them. The Built for Shopify badge explicitly verifies theme compatibility.
What happens when only some variants restock? Quality apps are variant-aware. A customer who signed up for "size M, blue" only gets notified when that variant returns, not when any version of the product restocks. We'd consider this a non-negotiable feature.
