Klaviyo vs Omnisend for Shopify Back-in-Stock Alerts
Why Back-in-Stock Alerts Matter for Small Shopify Stores
Every out-of-stock product page is a missed sale you can still recover. A shopper who lands on a sold-out variant, enters their email, and gets a one-time "it's back" notification is far more likely to buy than a cold subscriber — they already chose the product. For small stores that can't afford to overstock, back-in-stock alerts turn inventory gaps into a demand list instead of a dead end.
Klaviyo and Omnisend are the two most common email/SMS platforms for Shopify stores in this segment. Both support back-in-stock automations, but they handle setup, pricing, and scale differently. Here's how they actually compare.
Klaviyo Back-in-Stock Alerts: Setup and Features
Klaviyo's back-in-stock flow is built on its catalog and event tracking. When you connect your Shopify store, Klaviyo syncs your product catalog and receives "Placed Order," "Ordered Product," and related events. It also tracks a "Back in Stock" subscription event when a customer signs up for a notification on a sold-out variant.
Typical setup:
- Install the Klaviyo app from the Shopify App Store and connect the store.
- In Klaviyo, go to Flows → Create Flow → Back in Stock.
- The trigger is the "Back in Stock" metric (the customer's subscription to a specific variant).
- Add a time delay or a conditional split so the email only sends when the variant is actually in stock again.
- Customize the email with a product block that pulls the variant image, title, and price dynamically.
- Turn the flow live and test with a real out-of-stock variant.
Klaviyo's strength here is granularity. You can filter by variant, segment by past purchase behavior, and combine the back-in-stock flow with browse abandonment or winback sequences. It also supports SMS back-in-stock if you've collected SMS consent. The trade-off is that the flow builder is more complex — new users often need to read the documentation or watch a setup video.
Omnisend Back-in-Stock Alerts: Setup and Features
Omnisend takes a more guided approach. Its Shopify integration syncs products and orders, and it offers a pre-built Back in Stock automation in its Automation library.
Typical setup:
- Install the Omnisend app and connect Shopify.
- Go to Automation → Pre-built workflows → Back in Stock.
- Enable the workflow; Omnisend handles the trigger and the "product available again" condition.
- Edit the email template — Omnisend's editor is drag-and-drop with product blocks.
- Optionally add an SMS step if you're collecting phone numbers.
- Test with an out-of-stock product.
Omnisend's advantage is speed: most small stores can have a working back-in-stock email live in under an hour. It also bundles email and SMS in one workflow without needing separate consent logic beyond what the platform handles. The trade-off is less flexibility — advanced conditional logic and deep segmentation aren't as developed as Klaviyo's.
Pricing Comparison: Klaviyo vs Omnisend for Back-in-Stock Notifications
Both platforms price primarily by number of contacts (not emails sent) and offer a free tier for small lists. Back-in-stock automations are included in the standard plans on both — you don't pay extra for the flow itself.
| Factor | Klaviyo | Omnisend |
|---|---|---|
| Free tier | Yes, up to a contact limit | Yes, up to a contact limit |
| Pricing model | By contacts, monthly | By contacts, monthly |
| SMS pricing | Separate SMS credits | SMS credits included on some plans |
| Back-in-stock flow | Included | Included |
| Shopify integration | Native app | Native app |
| Best for | Segmentation-heavy stores | Stores wanting fast setup |
Because both change pricing regularly, check current pricing on each vendor's site before deciding. A useful test: calculate your cost at your current list size and at roughly double that, since back-in-stock flows tend to grow your list.
Automation Limits and Scalability for Growing Stores
The real difference shows up as you scale.
Klaviyo strengths: - Deep segmentation (RFM, predicted lifetime value, custom properties) - Complex flow branching and conditional splits - Robust API and webhook support for custom integrations - Better for stores running multiple flows that interact
Klaviyo limits: - Steeper learning curve - More setup time per flow - Costs can climb quickly as contacts grow
Omnisend strengths: - Fast, template-driven setup - Email + SMS in one workflow - Cleaner UI for non-technical owners - Good deliverability and reporting
Omnisend limits: - Less granular segmentation - Fewer advanced automation branches - Custom integrations are more limited
If you're a store doing under roughly a few thousand contacts and running simple flows, Omnisend's simplicity usually wins. If you're planning to run layered automations — back-in-stock plus browse abandonment plus post-purchase — Klaviyo's flexibility pays off.
Which Tool Should You Choose? Key Takeaways for Small Shopify Stores
- Choose Omnisend if you want a back-in-stock flow live today, prefer a guided setup, and don't need deep segmentation.
- Choose Klaviyo if you plan to grow into complex automations, run SMS and email together with detailed targeting, or need custom integrations.
- Either works for the core job: capturing a sold-out variant signup and emailing when it restocks.
- Test before committing. Both offer free tiers — set up a back-in-stock flow on a real out-of-stock product and see which interface you actually enjoy using.
- Watch list growth. Back-in-stock signups inflate your contact count, which affects your bill on both platforms.
A practical approach for many small stores: start with Omnisend if you're new to email automation, and migrate to Klaviyo once you're running three or more interacting flows or need segmentation that Omnisend can't deliver.
Conclusion
For most small Shopify stores, the back-in-stock feature itself is comparable on both platforms — the decision comes down to setup speed versus long-term flexibility. Omnisend gets you live faster with less friction, while Klaviyo rewards stores that invest time in segmentation and layered automations. Pick based on where you expect your store to be in 12 months, not just today.
FAQ
Q: Can I run back-in-stock alerts on both Klaviyo and Omnisend at the same time? A: Technically yes, but it's not recommended. You'd double-collect signups, split your data, and confuse customers with duplicate emails. Pick one platform as your source of truth.
Q: Do back-in-stock emails require SMS consent? A: Email alerts only need email consent. If you want to send the notification by SMS, you need separate SMS opt-in — both Klaviyo and Omnisend handle this within their SMS tools.
Q: What happens if a product never restocks? A: Both platforms let the flow wait for the in-stock condition. If it never triggers, the customer simply doesn't get an email. It's worth adding a fallback "still unavailable" email after a set number of days if you sell seasonal or limited items.