Forthcast works with Klaviyo

Direct answer: Forthcast sends reorder and delivery confirmation events to Klaviyo, triggering back-in-stock email flows when your inventory arrives. Your waitlist subscribers get notified automatically the moment new stock is confirmed, so you capture demand right when products become available.

Running out of stock is bad enough. Missing the window to notify eager customers when products return? That's leaving money on the table. This integration connects Forthcast's purchase order tracking with Klaviyo's email automation, so your back-in-stock notifications fire based on actual inventory events instead of guesswork.

When you confirm a purchase order in Forthcast, subscribers waiting for those products receive emails through their Klaviyo flows. No manual exports, no spreadsheet matching, no delay between when stock lands and when customers hear about it.

How it works

1. You confirm a purchase order in Forthcast for products that have waitlist subscribers in Klaviyo.
2. Forthcast sends a reorder confirmation event to Klaviyo containing the SKUs and expected delivery details.
3. Klaviyo matches the event data against your existing back-in-stock flow subscribers and triggers the appropriate email sequences.
4. When the inventory arrives and is marked as delivered in Forthcast, a delivery confirmation event fires, allowing you to send follow-up notifications or adjust messaging based on actual stock availability.

Why merchants use Forthcast with Klaviyo

• Timing matches reality. Your back-in-stock emails send when you've actually confirmed new inventory is coming, not based on estimated dates or manual triggers. Customers get accurate information, and you avoid the awkward situation of promising stock that hasn't been ordered yet.
• No manual list management. You don't need to export waitlists, cross-reference SKUs, or remember to trigger flows when purchase orders come in. The events pass automatically from Forthcast to Klaviyo, so your email automation runs without you touching it.
• Capture demand immediately. The moment you confirm a PO, waitlist subscribers know their desired product is coming back. This early notification means you're first in their inbox, before they find alternatives or forget they wanted the item.
• Better flow control. With both reorder and delivery confirmation events, you can build Klaviyo flows that adapt to your supply chain reality. Send a "coming soon" email when the PO is confirmed, then a "buy now" email when the delivery is marked complete and stock hits your warehouse.

Frequently asked questions

How do I set up the integration?

Install the Forthcast app from the Shopify App Store if you haven't already, then connect your Klaviyo account through the integrations section in Forthcast settings. You'll authorize Forthcast to send events to your Klaviyo account, and the connection handles event passing from that point forward. Make sure you have back-in-stock flows already built in Klaviyo so the events have somewhere to route.

How quickly do events sync between Forthcast and Klaviyo?

Events send to Klaviyo within seconds of confirming a purchase order or marking a delivery complete in Forthcast. Klaviyo processes the events according to their standard flow timing rules, so if your back-in-stock flow is set to send immediately upon receiving the event, subscribers will get emails within minutes. Any delays you see are typically from Klaviyo's flow settings or send throttling, not from the event transmission itself.

What happens if the integration gets disconnected?

If the connection between Forthcast and Klaviyo breaks, events stop passing and your back-in-stock flows won't trigger automatically. You'll see a warning in your Forthcast dashboard if the integration status changes. Reconnecting is the same process as the initial setup: authorize Klaviyo access through the integrations page, and event passing resumes. Events that would have fired during the disconnection period won't retroactively send, so you may need to manually notify waitlist subscribers for any POs confirmed while disconnected.

Do I need specific Klaviyo plan features for this to work?

You need a Klaviyo account that supports custom events and flows, which is available on all paid Klaviyo plans. The free tier has limitations on flow capabilities that might restrict how you use the reorder and delivery events. Your Forthcast subscription must be active, and you need waitlist functionality enabled to collect subscribers in the first place. The integration itself doesn't require special API access or developer involvement.

What happens if I confirm a purchase order that includes some SKUs with waitlists and some without?

Forthcast sends events for the entire purchase order, and Klaviyo filters subscribers based on which specific products they're waiting for. If a PO has 10 SKUs but only 3 have active waitlists, only subscribers waiting for those 3 SKUs receive notifications. The other 7 SKUs pass through the event data but don't trigger emails because no one is subscribed to those back-in-stock flows. This means you can confirm mixed purchase orders without worrying about irrelevant notifications going out.