A size and color waitlist stores the signup on the variant the shopper selected, not on the product as a whole. When that variant's available quantity crosses your stock threshold, only the people who asked for that size or color are emailed. SK Back In Stock's listing says customers can wait for the exact size or color. The catalog agrees: signups keep both the product ID and the variant ID, and the inventory webhook resolves to the variant that changed.
If you instead collect one email for "the jacket," you will write to people who wanted a different size when any size comes back. That is the failure this setup is meant to avoid. Make the shopper select the sold-out combination before they join.
One signup per variant
A product with three colors and six sizes is eighteen variants. Each can be in stock or not. A signup row points at one of those eighteen. The admin can group rows under the product title so the list is readable, and the variant is still on the row, with the email, the subscribed date, the status, and the notified date.
Status is waiting, notified, purchased, or unsubscribed. Purchased, in this app, means a later order matched the same email and the same variant. A customer who was waiting on medium and bought small does not satisfy that match. Your reorder notes should stay at variant level for the same reason. Fourteen requests for black in medium are not fourteen requests for black in every size.
The threshold is yours. The catalog default is 1, meaning the upward cross from out of stock into at least one available unit can send the alert. If black medium goes from 0 to 4, the people waiting on black medium are the queue. People waiting on black large stay waiting. Adding more units later, while the variant is already above the threshold, does not send another back-in-stock email.
What the shopper must select first
The button's visibility follows the variant selected on the page, and it updates when the shopper switches color or size, without a reload. If the block cannot see product data, it can load the product's public JavaScript endpoint.
Many themes preselect the first size. The shopper has to select the sold-out size before Notify Me applies to it. Write the popup so the combination is obvious.
- Select a sold-out color and an in-stock size. Confirm the page still sells that pair if the combination exists.
- Select the sold-out pair. Confirm Notify Me is the action for that pair.
- Join with your own email. In the admin, confirm the variant on the row is the pair you selected, not the product's first variant.
- Repeat on a second sold-out pair. You should see two rows, not one product-level row that forgot the size.
The catalog does not say the app blocks signup when no option has been clicked. It ties the signup to the variant the page currently has selected. Train the theme and the popup copy around that fact. Do not assume a shopper who never touches the size chart joined "whatever we have."
What the email should name
The person should be able to tell which item returned. The catalog's template placeholders are product name, product URL, new price, and old price. A separate variant-title token is not in that list. The send itself is still limited to people who signed up for the variant that crossed the threshold, so a large-size subscriber is not in the small-size queue. The words inside the email are a different question.
If the product-name placeholder prints only "Wool coat," a shopper who waited on rust, size 8, may not see rust or 8 in the message unless your template text supplies them. A single shared template with "size 8" typed in as permanent copy is wrong the moment a different size is restocked and the same template is used. Test two variants. Read both emails. If the body cannot name the option, fix the template before you promise shoppers it will.
Link the product URL placeholder to the product page. Do not invent a discount. Old price and new price are for real price values, not for a code. Do not promise a ship date the app does not know.
How this changes the reorder
Sort signups by variant before you talk to the factory. A product total hides the size people actually requested. Bring the waiting count, failed sends, and, if you have restocked before, the purchased count from the email-and-variant order match. The 30-day signup growth percentage does not choose the size run.
Case packs are your constraint. If the maker only sells a full run, the waitlist shows which sizes are pulling the request. Zero signups on a size does not prove zero demand. It proves nobody left an email for that size while the button was live.
When you receive goods, receive them onto the variant you promised. Stock posted to the wrong size will not cross the threshold for the people who are waiting, and stock posted to a size that is already available will not email the other list.
What this app does not claim
SK Back In Stock does not document a Notify Me button on collection cards. Configurations can target products in a collection, which only chooses where the product-page button applies. SMS, WhatsApp restock messages, and preorders are not in this catalog. Competitor listings have advertised those. They are not features to describe on this button.
Customer emails are not documented as a multi-language set. The admin interface is localized in English, German, and French. That translates the screens you use, not the restock email your shopper reads. Write the template in the language your buyers expect.
One email does not cover every color. A shopper who wants both the navy and the rust, if both are sold out, needs a signup on each variant. The catalog does not describe an "all colors" enrollment. Do not add that sentence to the popup.
Questions about variant waitlists
If the shopper does not pick a size, which list do they join?
They join the variant the page has selected at that moment. Check your theme's default selection. The catalog does not describe a separate "no size chosen" list.
Can one email cover every color?
Not as a documented feature. Each signup is one variant. Joining two colors means two signups.
Will the restock email name the size automatically?
The documented inserts are product name, product URL, new price, and old price. Confirm on a test send whether the size or color appears. Do not assume a variant-title token you have not seen.
Read SK Back In Stock if you want waitlists stored per size and color. Test two variants before you tell shoppers the email will name the option they picked.