What Is a Klaviyo Back in Stock Flow, and Is It Worth Building?

A Klaviyo back in stock flow is an automated email or SMS sequence that notifies a customer when a product they asked to be alerted about is available again. It is worth building for any ecommerce brand that sells out of products customers actively want, because the demand already exists. The flow does not create demand. It stops you from losing it.

Should we build a back in stock flow?

Founders usually ask this right after a bestseller sells out and the customer service inbox fills up with "when is it coming back?"

Or they ask the opposite: "We rarely sell out. Do we even need one?"

Both are fair questions. But the real question is not whether back in stock flows work.

It is how often your customers want something you cannot currently sell them.

By Emiel Dingemans, Founder of Magicianly

What Is a Back in Stock Flow?

A back in stock flow is an automation that waits for a sold-out product to return and then alerts the customers who asked to be notified.

It reacts to one specific signal: a customer wanted a product, could not buy it, and asked to be told when they can.

In Klaviyo, the sequence works like this:

1. 1A customer submits a "notify me" form on an out-of-stock product or variant page.
2. 2Klaviyo records a Subscribed to Back in Stock event on their profile.
3. 3The flow holds them at a back in stock delay.
4. 4When the item is restocked, they move to the next step, usually an email and sometimes an SMS.

Klaviyo documents this setup for Shopify, BigCommerce, Magento 2, PrestaShop, Salesforce Commerce Cloud and Shopware, and for inventory-aware custom catalogs. See the Klaviyo Help Center guide to building a back in stock flow for current platform details.

How Is a Back in Stock Flow Different From Other Flows?

A back in stock flow starts with intent the customer has already stated. Most other flows have to build that intent.

Compare it with the abandonment journeys:

That last row changes everything.

A back in stock subscriber is not a window shopper. They are a customer waiting for you.

So the job of the flow is not persuasion. It is speed and clarity.

You do not need to manufacture urgency either. If inventory is limited, the urgency is already real.

If you want to see how the lower-intent version should work, read our guide to the Klaviyo browse abandonment flow.

Is a Back in Stock Flow Worth Building?

For most ecommerce brands that sell out of products, yes. Its value depends almost entirely on how often you go out of stock on products people actually want.

A brand that sells out of a few slow-moving variants a year will collect a small number of restock alerts.

A brand whose bestsellers regularly sell out, or that runs limited drops, may have a flow that quietly captures meaningful demand every month.

Benchmarks will not tell you which of those you are. Your own data will.

Before deciding, look at:

• how often products went out of stock in the last 12 months;
• whether those were bestsellers or long-tail variants;
• how long they typically stayed unavailable;
• how many customers contacted support about restocks;
• whether you currently capture that interest at all.

If the answer to the last question is no, you are losing demand you already paid to create.

Where Does a Back in Stock Flow Sit in Your Flow Priority?

A back in stock flow is a supporting flow. For most brands it comes after the core lifecycle flows, unless sell-outs are a regular part of the business.

If nothing is set up properly yet, we generally build the core first:

1. 1Welcome
2. 2Checkout abandonment
3. 3Cart abandonment
4. 4Browse abandonment
5. 5Post-purchase
6. 6Winback

Those carry most of the volume because they touch most of your customers. We explain that order in Ecommerce Email Flows: The Automations That Actually Matter.

Back in stock earns its place afterwards for a simple reason. Once it is built, it runs on its own, on an audience that rebuilds itself every time you sell out.

For brands built around drops, limited batches or frequent sell-outs, it can deserve a much earlier slot. The priority should follow your inventory reality, not a template.

How Do You Set Up a Back in Stock Flow in Klaviyo?

Setting up a Klaviyo back in stock flow takes five decisions: how you capture the signal, the trigger, notification batching, the restock minimum and exclusions. The build is simple. The decisions matter more.

1. Capture the signal on the product page

You need a visible "notify me when available" option on every out-of-stock product and variant page.

If customers cannot easily raise their hand, the flow has nothing to work with.

Make it work per variant. Someone waiting for a size medium does not want an alert about a size large.

2. Trigger on the Subscribed to Back in Stock event

The flow starts when the restock alert is submitted. The back in stock delay then holds the customer until the item is available.

3. Decide how many people to notify per unit

This is the setting most brands never look at.

Klaviyo can notify customers in batches based on available inventory, with a wait time between batches, instead of alerting everyone at once.

Why does that matter? If many people are waiting and only a handful of units come back, notifying everyone at the same time sends most of them to a sold-out page again.

You turn a customer who wanted your product into a customer who feels let down twice.

Batching protects that experience. Start with a number that gives everyone notified a realistic chance to buy, then adjust based on how quickly restocks sell through.

4. Set a sensible restock minimum

A minimum inventory threshold stops alerts from firing when only one or two units return.

Set it too high, though, and small restocks never notify anyone while the waiting list slowly loses interest.

Set it around the smallest restock you would genuinely want customers to know about.

5. Add exclusions

Remove anyone who already purchased the item since subscribing. Nobody should receive "it is back" for a product they already bought.

What Should a Back in Stock Email Say?

A back in stock email should say one thing clearly: the exact product the customer asked about is available, and here is the link. The customer already knows the product. They asked for this message.

A strong back in stock email usually needs:

• a subject line that says the product is back;
• the product image and the exact variant they asked about;
• one primary CTA, near the top, straight to the product page;
• honest stock information if inventory is genuinely limited;
• optionally, one short line of reassurance, such as a review.

That is it.

This is not the place for a brand story, five other product recommendations and a newsletter section underneath. Every extra element adds friction between a customer who wants to buy and the product they want. Our email design best practices explain why one clear action wins.

Plain text can work well here too. A short, personal "the one you were waiting for is back" often feels more like a service than a campaign.

Should Back in Stock Emails Include a Discount?

Generally, no. The customer asked to be notified, so they already want the product at its current price.

A discount here mostly gives away margin on demand you already had.

It can also teach customers something unhelpful: waiting is rewarded.

The incentive is availability itself.

How Many Emails Should a Back in Stock Flow Send?

Start with one email sent immediately on restock. Add a second only if your restocks last long enough for it to make sense.

• Email 1: immediately on restock. The entire value of the message is being early.
• Optional follow-up: roughly a day later, only to people who did not click or purchase, and only if the item is still in stock.

If a restock usually sells out within hours, a follow-up is pointless. If stock holds for days, one gentle reminder is reasonable.

What we do not recommend is a long chain of reminders for a product someone already knows they want. That is repetition, not persuasion.

Should You Send Back in Stock Alerts by SMS?

Yes, for customers who have given SMS consent, a restock alert is one of the clearest SMS use cases there is.

Our default at Magicianly is to use promotional SMS mainly for launches, restocks and sales or events where the urgency is real. A restock of a product someone explicitly asked for, with limited inventory, fits that rule exactly. We explain the wider approach in SMS Marketing Best Practices for Ecommerce.

A few principles:

• only text customers who have given SMS consent;
• keep the message short: product, variant, link;
• use SMS for limited, fast-selling restocks, and email for slower ones;
• do not send the same alert by email and SMS at the same moment unless the restock genuinely justifies both.

The point is not to use every channel because you can. It is to use the fastest channel when speed actually matters.

Can You Use Back in Stock Demand Beyond the Flow?

Yes. Back in stock subscribers are a live demand signal that can inform inventory and campaign planning, not just the flow.

They can tell you:

• which products and variants are under-stocked;
• how much demand exists before a restock lands;
• which items deserve a dedicated restock campaign to your engaged segment.

A major restock of a popular product is a legitimate campaign moment for your wider engaged audience, alongside launches and product-focused campaigns in your ecommerce email marketing calendar.

That is a genuine reason to email. Not a manufactured one.

How Should You Measure a Back in Stock Flow?

Measure a back in stock flow on how many waiting customers actually buy, not only on Klaviyo attributed revenue.

Look at:

• restock alert sign-ups per product and variant;
• conversion rate from alert to purchase;
• time from notification to purchase;
• how often notified customers hit a sold-out page again;
• unsubscribes and complaints on the flow;
• whether restock buyers go on to make a second purchase.

If many notified customers cannot buy, your batching is wrong, not your customers.

What Are the Most Common Back in Stock Flow Mistakes?

The most common mistake is not capturing restock interest at all. The others mostly come from notifying the wrong people, at the wrong time, with too much in the email.

1. 1No notify-me option on out-of-stock pages.
2. 2Notifying everyone at once when only a few units are available.
3. 3Alerting customers about the wrong variant.
4. 4Adding discounts to demand that already exists.
5. 5Filling the email with content that distracts from the one action.
6. 6Sending reminders after the product has sold out again.
7. 7Using scarcity language when stock is not actually limited.

So Is a Klaviyo Back in Stock Flow Worth Building?

If you sell out of products customers want, yes.

It is one of the few flows where the customer has already told you exactly what they want and asked you to get in touch.

Build it once. Capture the signal properly, notify in sensible batches, keep the message short and let availability do the selling.

You do not need to create demand here. You only need to avoid wasting it.