Best back in stock app for Shopify, compared by real cost and limits

Every Shopify store sells out of something, and a signup on the sold-out page turns lost visits into a waiting list. Most roundups rank apps by widget design. What decides your bill is the notification limit, the price of SMS, and whether the app stops a small restock from selling out in minutes.

• A few sold-out products, email only. Start on a free plan. Amp allows 10 notifications a month and STOQ 30 emails a month, which is enough to test demand.
• A store that restocks often. Pay for a plan sized to notifications, not to features. Amp Starter is 19 USD for 500 notifications and STOQ Lite is 10 USD for 1 000 email and SMS messages.
• A store that wants alerts by text. Check the SMS price before you pick. STOQ charges 0.025 USD per text on top of the plan. Amp prices SMS by destination country.
• A store that already pays for several recovery tools. Consider one platform that runs back in stock, cart, checkout and payment recovery, so consent and message frequency are managed in one place.

Prices below come from each app's Shopify App Store listing, checked on 2026-10-31. Plans are billed every 30 days in USD.

Klaviyo lists back-in-stock emails as a campaign type, but its listing does not say which plan includes it, so confirm that with Klaviyo before you count on it.

Say a store restocks three products a month and 800 shoppers are waiting across them. Each alert is one notification, so you need about 800 notifications a month.

On Amp that is above the Starter limit, so Growth at 49 USD per month. On STOQ, Lite at 10 USD covers 1 000 email and SMS messages, but if half the list wants a text, the SMS fee adds 400 times 0.025, so 10 USD more. On Klaviyo the cost follows your total contacts, not the alerts.

On CartAbandon the same store pays for Growth, 149 USD per month or 74 USD billed yearly, and the alerts are one part of a plan that also recovers carts, checkouts and price drops.

Here is the honest part. If back in stock is the only thing you need, STOQ and Amp are cheaper than we are, and you should start there. The case for a platform is a store that already loses orders to abandoned carts and declined cards, because the same plan covers all of it.

1. Variant level signups. A shopper wants the medium, not the product. Check that the signup shows only on the sold-out size or color.
2. Notification order and throttling. Alerting 600 people about 40 returned units sends hundreds to an empty page. Look for alerts in signup order and in batches.
3. Channel consent. Email, SMS and WhatsApp each need their own opt-in, with a record of source and time.
4. SMS price. A per-text fee on top of the plan changes the math for fast-selling items.
5. Demand data. A list of who is waiting for which variant tells you what to reorder first.
6. Theme impact. The signup should load without slowing the product page.

Our back in stock alerts page shows how CartAbandon handles each of these, including how a small restock is throttled to your stock.

A restock is a moment worth announcing beyond the waiting list. Many stores paste the product link into an AI ad generator that turns a product link into hooks, scripts and video and run a short campaign the day the item returns, while the waiting list gets its alerts first.

Choose STOQ or Amp free if you are testing demand on a small store. Choose Amp if you also want preorders. Choose Klaviyo if your whole email program already lives there. Choose CartAbandon if you want back in stock alerts, abandoned cart and checkout recovery, price drop alerts and failed payment recovery on one flat plan with texts and WhatsApp included. See CartAbandon plans or the Shopify abandoned cart app page.