A free back in stock app for Shopify that never caps your subscriber list
Kelso emails your customers when an out-of-stock product comes back. The free plan is $0 a month, no credit card needed to install, and it never limits how many people can join your waitlist. What it does limit is alert sends, 50 a month, which is plenty for a store just getting started.
Free to install. Plans from $0, upgrade only if you outgrow it.
The first 50 stores to install lock today's price for as long as they stay subscribed. No countdown, the count is real.
Free means free, not a trial
- $0 a month, no credit card to install. Add Kelso from the Shopify App Store and start collecting signups the same day.
- 50 alert sends a month. A send happens when a restocked product emails one subscriber. 50 sends covers a slow month for most small stores.
- Unlimited subscriber capture, forever. Your waitlist is never capped and never costs anything to grow, on the free plan or any paid plan.
- Full variant-level tracking. Someone waiting on the medium in green only hears about the medium in green coming back, not every restock of the product.
- One ESP integration. Connect Klaviyo or Mailchimp and Kelso fires subscribe and restock events into your existing flows.
- Sends hold, they never drop. Go over 50 in a month and alerts queue up instead of failing to send. The queue releases when you upgrade or the month resets.
What the free plan doesn't include
50 sends a month is the one real limit. It's a cap on alert emails, not on signups, so your waitlist keeps growing even in a month where you don't send a single alert. Once a restock pushes you past 50 sends in a month, the extra alerts hold in a queue instead of failing, and they go out as soon as you upgrade or the month resets.
If your store restocks often enough that 50 sends stops covering you, Starter is $14/mo for 750 sends, flat, no revenue share and no overage fees on any plan. The pricing page breaks down all four tiers and includes a calculator so you can check your own numbers before you upgrade.
How Kelso's free plan compares
We're not going to tell you Kelso has the biggest free plan in the category, because it doesn't. Here's where things actually stand, based on what each app lists on its own Shopify App Store page:
| App | Free plan |
|---|---|
| Kelso | 50 sends/mo, unlimited subscriber capture |
| Ordersify | 100 notifications/mo |
| Appikon | 10 emails/mo |
| Amp | 10 notifications/mo, unlimited signups |
| STOQ | 10 preorders + 30 emails/mo |
| Notify! | 10 restock notifications/mo |
| Swym | No free tier (removed in 2026) |
Competitor free-tier details as listed on each app's Shopify App Store page, July 2026. Pricing changes, check the listing for current numbers.
Ordersify's free plan allows more notifications a month than ours, and we'd rather say that plainly than pretend otherwise. Where Kelso is honestly different: your subscriber list is never capped no matter which plan you're on, the price is set by sends instead of contacts, and sends that go over the limit hold in a queue instead of getting dropped. Swym removed its free tier entirely in 2026, so if you're comparing options, Kelso, Amp, Appikon, STOQ, Notify!, and Ordersify are the free plans still standing.
Already running a different app?
Moving to Kelso doesn't mean starting your waitlist from zero. Export your current list as a CSV and it comes in with subscriber picks intact. See how migrating to Kelso worksfor the full walkthrough.
Questions about the free plan
Is Kelso really free?
Yes. The free plan is $0 a month with no credit card needed to install. You get 50 alert sends a month, unlimited subscriber capture, full variant tracking, and one ESP integration (Klaviyo or Mailchimp). Nothing about signing merchants up is a trial, it stays free for as long as you want to stay on it.
What happens when I hit 50 sends?
Sends hold. They're never dropped and never billed as an overage. Once you're queued up, alerts wait until you upgrade or your month resets, then they go out. If you're consistently near the limit, the next plan up is Starter at $14/mo for 750 sends, see the full breakdown on the pricing page.
Do I lose my subscriber list on the free plan?
No. Subscriber capture is unlimited on every plan, including free. You can collect as many signups as your store gets, forever, and only pay for the emails that go out when a product restocks. If you outgrow the send limit, upgrading does not touch your existing list, it just raises how many alerts can go out.
How is this priced compared to other apps?
Kelso is priced by how many alert emails you send, not by how many contacts or subscribers you have. That's different from most marketing platforms, where a growing list can quietly push you into a higher tier even in a slow month. Paid plans start at $14/mo for 750 sends, $29/mo for 3,000, and $59/mo for 10,000, flat, with no revenue share and no overage fees.
Install free, upgrade only if you need to
No credit card, no trial clock. Start on the free plan and see if 50 sends a month covers you before spending anything.
Free to install. Plans from $0, upgrade only if you outgrow it.
The first 50 stores to install lock today's price for as long as they stay subscribed. No countdown, the count is real.