Back in Stock

The back-in-stock flows turn a sold-out product into a recovered sale. A customer who missed out leaves their WhatsApp number on the product page; when you restock the item, WhatPro sends them a message so they can return and buy before it sells out again.

There are two related flows:

• Back in Stock — the core restock alert.
• Back in Stock Follow-up — an optional second message, typically carrying a discount code, sent after a configurable delay to nudge customers who haven’t bought yet.

Both can run independently. With both enabled, a customer receives the first alert when the product returns, and the discounted follow-up later if they still haven’t converted.

How customers subscribe

Subscriptions are collected on the storefront, not from inside the order flow.

1. Add the WhatPro — Back in Stock theme block to the product template (inside the Product information section, above the Add to cart row).
2. The block stays hidden while the selected variant is in stock. When a variant is sold out and inventory-tracked, it shows a Notify me when available button in place of the disabled Sold out button.
3. Tapping the button opens a popup asking for the customer’s WhatsApp number (and, optionally, their name).
4. On submit, WhatPro records an inventory watch for that customer and variant.

Guest numbers can be verified with a WhatsApp OTP before the watch is recorded (a per-block setting); logged-in customers skip verification. Allowed phone-number countries follow the Back in Stock flow’s country settings — lock to shop country, a specific list, or any country. When only one country is allowed, the popup collapses to a static dial-code chip.

All customer-facing text on the block and popup is translated once per shop via the WhatPro Back in Stock App embed and Shopify’s Translate & Adapt. See Languages.

Trigger

The restock detection is inventory-driven, not order-driven:

1. When inventory for a watched variant rises above zero, Shopify fires an inventory webhook.
2. WhatPro finds the open watches for that variant and marks them ready.
3. A batched send job is enqueued per enabled flow variant, honoring each flow’s delay.
4. When the job fires, it sweeps every ready watch for the customer, so several products that restocked within the same window are combined into a single message rather than one message per product.

Because the alert is a marketing message, it is suppressed for customers who have opted out of WhatsApp marketing (for example, anyone who replied STOP).

Note

The Back in Stock Follow-up runs after a delay measured from the restock. WhatsApp enforces a minimum window for this kind of follow-up message; if you configure a shorter delay, WhatPro raises it to the allowed minimum automatically.

Key variables

The restock alert is built from product and customer data resolved at send time.

Variable	Description
customer_first_name	Customer’s first name; falls back to a generic greeting when unknown.
product_title	The restocked product’s title. For multi-product sends, the message uses a carousel card per product.
price	The product’s current price, fetched live at send time.
compare_at_price	The compare-at price, when set.
product_url	Link to the restocked product page (single-product send) or the shop homepage (multi-product send).
product_count	Number of products in the send.

The Back in Stock Follow-up flow adds discount variables when you enable a discount code on it:

Variable	Description
discount_code	The discount code delivered with the follow-up.
discount_value	The discount amount (for example 10%).

Multiple restocked products are delivered as a WhatsApp carousel — one card per product with its image, title, price, and shop link.

Plan availability

Both back-in-stock flows are available on Growth and Plus. Starter and Basic do not include them. See Plans.

Tags

The back-in-stock flows are not part of the order lifecycle tagging system; they are driven by product restocks rather than orders. When a back-in-stock customer returns and places an order, WhatPro attributes that order back to the alert so you can measure recovered revenue. For how WhatPro tags orders and customers in general, see Order tags.

Related

• Storefront: Checkout Gate — the OTP pipeline the back-in-stock popup reuses to verify guest numbers.
• Flow overview
• Languages