How to Sync Shopify Popup Signups With Klaviyo and Shopify Email

A popup that collects emails but does not send them anywhere is a leaky bucket. The shopper expects their discount right away. If the welcome email arrives the next day, or not at all, you lose the moment.

Here is how to connect your popup to the two tools most Shopify stores use, and what to send along so the data is useful later.

Data note: Integration figures come from aggregated, anonymous PopupBoost data as of November 2026.

What PopupBoost stores connect to

Among stores with an active integration in PopupBoost:

• 73 sync signups to Shopify customers
• 37 sync to Klaviyo
• 5 sync to Omnisend
• 1 syncs to Mailchimp

Shopify customers is the most common because it is built in and feeds Shopify Email directly. Klaviyo is the most common dedicated email platform.

How syncing to Shopify Email works

Shopify Email sends to customers whose email marketing status is subscribed. So the job of a popup integration is to create or update the Shopify customer and set that status when the shopper has given consent.

PopupBoost does exactly that. It also follows one important rule: it never re-subscribes a customer who has unsubscribed. That choice belongs to the shopper.

Since 2024, Shopify also lets apps trigger its "Customer subscribed to email marketing" automation. That means a signup from your popup can start the welcome email or welcome series you build in Shopify, with no extra tool.

Set it up

1. In PopupBoost, open the integrations section and enable the Shopify customers sync.
2. Turn on customer tags so you can see which campaign and prize each subscriber came from.
3. In Shopify, go to your marketing automations and create a welcome automation that uses the "Customer subscribed to email marketing" trigger.
4. Put the discount code logic in the email, or send shoppers back to the store, where won codes can auto-apply.
5. Test with your own email address.

How syncing to Klaviyo works

Klaviyo gives you more control. You can send signups to a specific list, add properties to each profile and build flows based on them.

PopupBoost can send each subscriber to a Klaviyo list, tag them with the prize they won, and even send different prizes to different lists. It also passes traffic attribution (UTM parameters and referrer) so you can see which campaigns bring subscribers who buy.

Set it up

1. In Klaviyo, create a private API key with access to lists and profiles.
2. In PopupBoost, open the Klaviyo integration, paste the key and choose your list.
3. Optional: set a different list or tag per wheel slice, for example "won-free-shipping".
4. In Klaviyo, build a welcome flow triggered by "Added to list".
5. Use the prize tag to send each subscriber an email that matches the reward they won.

Our help article on the Klaviyo integration has screenshots for each step. If you use Omnisend, see the Omnisend guide.

What data to send along

An email address alone is a thin record. These extra fields make later campaigns much smarter:

• Prize won. Send a reminder before the code expires, only to people who have not used it.
• Campaign name. Compare subscribers from your welcome wheel with those from your BFCM campaign.
• Source page. Know whether people signed up on the homepage, a collection or a landing page.
• UTM and referrer. Connect signups back to the ad or post that brought them.
• Phone number, if collected, for SMS. Read collecting phone numbers for SMS.

Common sync problems and how to avoid them

In PopupBoost, 92.7% of real-time subscriber syncs succeed on the first try. When a sync does fail, the cause is usually one of these:

• Expired or replaced API key. Someone rotates the key in Klaviyo and forgets the popup app. Update it in both places.
• Deleted or renamed list. The popup still points to the old list. Check the list after any cleanup in your email tool.
• Double opt-in. With double opt-in on, new profiles stay pending until they confirm. That is correct behavior, but it can look like a failed sync.
• Invalid phone format. Numbers without a country code are often rejected by SMS tools.

When you change anything in your email platform, send a test signup through the popup and check that it arrives.

Avoid sending the welcome email twice

If you connect both Shopify customers and Klaviyo, decide where the welcome email lives. If both tools send one, the shopper gets two emails with the same code. Shopify itself recommends that apps make merchants aware of this.

A simple rule: let Klaviyo send marketing emails, and let the Shopify sync keep your customer records and tags up to date.

Your next step

Open your popup app today and check three things: the integration is active, the last sync was recent, and a test signup arrives in your list within a minute. Then check your welcome email and make sure the prize the shopper won is in it.

If you are still building the list itself, read how to build an email list on Shopify from zero.

Frequently asked questions

Can a popup app add subscribers to Shopify Email?

Yes. Shopify Email sends to customers whose email marketing status is subscribed. When PopupBoost syncs a signup to Shopify customers with consent, the customer is marked as subscribed and appears in your Shopify Email audience. It never re-subscribes someone who unsubscribed.

Should I use Klaviyo or Shopify Email for popup signups?

Shopify Email is simple and built in, which suits smaller stores. Klaviyo gives you deeper segmentation and flows, which pays off as the list grows. Many stores send signups to both: Shopify customers for the store record, and Klaviyo for marketing.

Why are my popup signups not showing up in Klaviyo?

The most common causes are an expired or replaced API key, a list that was deleted or renamed, and a double opt-in setting that keeps new profiles pending until they confirm. Check the integration status in your popup app first, then the list settings in Klaviyo.