Collecting the request needs no app
A back-in-stock request has two halves. Collecting it — an email address and which size it is for — is a form, and Shopify already has the forms. Sending the email when the size comes back is a job for something that sends: Shopify Flow, Shopify's email automations, or an app.
This block does the first half, through one of Shopify's two storefront forms, chosen in the theme editor:
- As a message to you (the default). The request reaches your store's inbox like any contact message, naming the product, the size, its SKU and a link to it. Nothing to set up, and nobody is subscribed to anything.
- As a customer. The address is saved on a customer tagged
restockandrestock-<variant id>, for a workflow or a customer segment to find. Shopify gives a theme no way to tag a customer without subscribing the address to email marketing, so the form says so in so many words, beside the button.
On the product page
The form appears under a size that is sold out and nowhere else, and the confirmation takes its place when the request is sent — before any script loads, or without one.
On a phone, pressing a sold-out size raises the form as a sheet over the page rather than growing it under a buy button that is already off screen, and the sheet offers the sizes either side that are in stock. From a tablet up it is the same form in place.
It never shows under a product you have marked as not made again. And on Hullara Drop, a release that has not opened yet shows the same form asking to be reminded when it opens (launch countdown).
Sending the email when it is back
Shopify Flow has a trigger for exactly this moment, Product variant back in stock: it starts a workflow when a variant's stock goes from zero or less to one or more, on a product whose inventory is tracked. From there:
- To tell yourself, Flow's Send internal email action writes to the addresses you type in — it is meant for staff.
- To tell the shopper, the Shopify Messaging connector's Send Marketing Email action sends to customers subscribed to email marketing, which is why the customer option subscribes them.
All three read on the Shopify Help Center, 21 October 2026. Which customers asked for which size is in their tags; the workflow that finds them and sends the email is yours to build, and we have not built it on our demo store.
What still needs an app
- An email that sends itself with no workflow to build. That is most of what a back-in-stock app sells.
- Text messages and push notifications, and counts of how many people are waiting for each size.
- A deposit on a pre-order. Hullara takes pre-orders through Shopify's own keep-selling setting; a deposit or a part payment needs an app.
Which themes have it
Every Hullara theme, in Pro. Hullara Apparel, for clothing stores, places it right under the buy button, below the size picker and its size chart, so a shopper who picks a sold-out size finds the form where they were about to buy.