Tell customers the second it's back
Kelso emails your customers the moment out-of-stock products come back, so you stop losing sales to a restock nobody heard about. Every alert is tracked, one price, no surprises later.
The first 50 stores lock today's price for as long as they stay subscribed. Joining the waitlist holds your spot.
- BIS-0138QUEUED → SENT → DELIVERED1.8s
- BIS-0139QUEUED → SENT → DELIVERED2.4s
- BIS-0140QUEUED → SENT → DELIVERED1.6s
- BIS-0141QUEUED → SENT → DELIVERED3.0s
- BIS-0142QUEUED → SENT → DELIVERED2.1s
- BIS-0143QUEUED → SENT → DELIVERED1.9s
- BIS-0144QUEUED → SENT → DELIVERED2.7s
- BIS-0145QUEUED → SENT → DELIVERED1.5s
- BIS-0146QUEUED → SENT → DELIVERED2.2s
- BIS-0147QUEUED → SENT → DELIVERED1.7s
- BIS-0148QUEUED → SENT → DELIVERED2.9s
- BIS-0149QUEUED → SENT → DELIVERED2.0s
- BIS-0138QUEUED → SENT → DELIVERED1.8s
- BIS-0139QUEUED → SENT → DELIVERED2.4s
- BIS-0140QUEUED → SENT → DELIVERED1.6s
- BIS-0141QUEUED → SENT → DELIVERED3.0s
- BIS-0142QUEUED → SENT → DELIVERED2.1s
- BIS-0143QUEUED → SENT → DELIVERED1.9s
- BIS-0144QUEUED → SENT → DELIVERED2.7s
- BIS-0145QUEUED → SENT → DELIVERED1.5s
- BIS-0146QUEUED → SENT → DELIVERED2.2s
- BIS-0147QUEUED → SENT → DELIVERED1.7s
- BIS-0148QUEUED → SENT → DELIVERED2.9s
- BIS-0149QUEUED → SENT → DELIVERED2.0s
Sold out is not lost, it's a waitlist
A "Notify me" button goes on your out-of-stock product pages. Customers sign up for the exact variant they want. You restock, Kelso emails them. That's the whole loop.
Storefront widget
A "Notify me" button that matches your theme. Theme block on OS 2.0 themes, snippet on older ones. You set the copy and colors.
Variant-level matching
Customers pick the exact size and color they want. Medium comes back in green, only those people hear about it.
Two-path detection
A webhook fires the moment your stock changes. A backup check runs behind it and catches whatever Shopify drops.
Paced sending
Alerts go out in batches you control, not one giant blast. That's what keeps your emails out of the spam folder.
Works with your ESP
Kelso can fire events into Klaviyo, Mailchimp, or Omnisend and let your own flows handle the sending. Or just let Kelso send for you.
One-CSV migration
Leaving another app? Upload one CSV and your subscribers, products, and variants come with you.
EU compliance
Double opt-in is a toggle, on by default for EU stores. We handle the Shopify GDPR webhooks so you don't have to think about it.
Demand analytics
See which products your customers are actually waiting on, plus sent, opened, clicked, and recovered revenue.
Most restock alert apps break
Read the one-star reviews in this category and the same three failures show up again and again. They're the reason stores switch apps.
Curious what a missed restock actually costs?Try the free stockout cost calculator.
Webhooks get dropped
Shopify doesn't guarantee webhook delivery. Apps that rely on webhooks alone fall out of sync, and nobody notices until a customer complains.
Big sends get flagged
Blast 500 emails at once and mailbox providers start blocking you. Your biggest restock is the one most likely to fail.
No record of what happened
Most apps can't tell you if a specific customer got their email. When something breaks, all you get is a guess.
Built to not break
- Two detection paths. The webhook fires first, for speed. A scheduled check runs behind it and catches anything the webhook drops.
- Paced sends. Alerts go out in batches you control, through a warmed sending domain.
- A full audit log. Every alert is tracked from queued to sent to delivered to clicked. Ask about any send and we'll show you exactly what happened.
- Flat pricing. One monthly fee. Go over your limit and sends hold instead of dropping.
- Human support. A person replies in hours, not days. That person built the app.
One email with one job
Your product, a photo, and one button back to the product page. No upsell blocks, no footer of links fighting for the click.
Want your own templates instead? Kelso fires events into Klaviyo, Mailchimp, or Omnisend and your flows handle the sending.
Built, submitted, and launching this month
There's nothing to install yet, so the waitlist is the whole ask. Join it and you'll get one email the day the listing goes live. Early stores also get free migration: send us a CSV and we'll move your waitlist over by hand.
- App builtCode complete and tested(done)
- Shopify reviewIn progress right now
- Live on the App StoreThis month
Flat pricing, from free
You pay for alert emails sent, nothing else. Subscribers, variants, and integrations are unlimited on every plan.
Common questions
How long does setup take?
Install the app, add the widget in your theme editor, and you're live. Most stores finish in under 5 minutes.
Will it work with my theme?
Yes. On OS 2.0 themes the widget is a native app block. On older themes you paste in a snippet. If it doesn't look right, email us and a person will fix it with you.
What happens if I go over my send limit?
Sends hold, they're never dropped. Alerts queue up, we let you know, and the queue releases when you upgrade or your month resets.
Can I migrate from Appikon, Swym, Amp, or another app?
Yes. Export your waitlist from your current app as a CSV and upload it in Kelso. Subscribers and their variant picks carry over. No export option in your old app? Email us and we'll help you find a path.
Does it work with Klaviyo?
Yes. Kelso fires subscribe and restock events into Klaviyo, so your own flows can do the sending while Kelso runs the widget and detection. Mailchimp and Omnisend work too.
Do you support double opt-in for EU customers?
Yes. Double opt-in is a toggle on paid plans, and it defaults to on for EU storefronts. Subscribers confirm by email before they join your waitlist.
Do you charge a revenue share or overage fees?
No. You pay a flat monthly price for a send allowance. No revenue share, no per-order fees, no surprise charges.
What happens to my waitlist if I downgrade or cancel?
Downgrading never deletes your waitlist. Subscriber capture is unlimited on every plan, including Free. Only send volume is gated. If you uninstall, your data is deleted per our privacy policy.
Stop losing restocks
Join the waitlist and get one email on launch day. Got questions first? Email us, a person replies in hours.
The first 50 stores lock today's price for as long as they stay subscribed. Joining the waitlist holds your spot.