Most ecommerce brands treat their sign-up form as a one-and-done pop-up. They drop a basic template on the homepage, offer 10% off, and wonder why their list growth stalls or why their mobile conversion rates look dreadful. That is a mistake.
A proper on-site capture system relies on distinct forms tailored to where the visitor is in their journey and what device they are using. Here is exactly how we build and configure these forms inside Klaviyo to maximise conversions without breaking user experience.
1. Build Your Master Desktop Form with Zero-Party Data
Always start by building your primary desktop pop-up first. We design all forms in Figma beforehand, matching brand fonts, paddings, and colour palettes so the on-site experience feels completely native.
When styling the form in Klaviyo, set your background image to cover the entire container and adjust input heights (55px is a solid baseline for clean click targets). Avoid harsh default borders and use transparent input backgrounds if your aesthetic calls for it. Focus heavily on padding and alignment rather than relying on standard presets.
For the second step of the form, collect zero-party data before revealing the discount code. Create custom profile properties first (such as customer preferences or product interests), then map your form buttons to assign these values upon clicking. Once submitted, display a success screen featuring a dynamic coupon code with an auto-apply button for Shopify or WooCommerce.
2. Clone and Reformat for Mobile (Never Use Auto-Responsive)
Never rely on a single responsive form to handle both desktop and mobile traffic. Klaviyo allows you to set device targeting for a reason. Desktop layouts with heavy side images or wide horizontal margins look broken on mobile screens.
Clone your master desktop form, rename it clearly with a mobile suffix, and switch the display setting to mobile-only. From there, strip out unnecessary horizontal padding, reduce font sizes, and stack your input fields cleanly.
Mobile users need frictionless tap targets. Adjust the input field padding so buttons are easy to press without accidental zooming. Once the mobile version matches your design specs, verify your form behavior settings match the primary campaign.
3. The Product Page Flyout Variant
A full-screen pop-up on a product detail page (PDP) is aggressive and often interrupts high-intent shoppers who are already evaluating an item. Instead, use a subtle flyout form on product pages.
Clone your base form, change the form type to a flyout, and adjust the targeting rules:
- Target the form to only appear on URLs containing /products/.
- Exclude the homepage.
- Set a timed delay of roughly 10 to 15 seconds to give users time to read the product description.
This captures interest from direct paid traffic landing straight on product pages without destroying your conversion rate.
4. The Discount Reminder Flyout for Unconverted Leads
Here is a tactic most brands miss entirely: targeting people who signed up for your welcome offer but have not actually purchased yet.
Create a segment in Klaviyo for subscribers who are opted into email marketing but have zero placed orders on their history. Then, build a dedicated discount reminder flyout specifically for this group.
This form should be single-step with no email input required. It simply acts as a visual prompt displaying their discount code, paired with a button that auto-applies the code to their cart and closes the modal. Set the targeting behavior to show after a 20-second delay, but only to visitors who have returned 4 days after their initial sign-up. It acts as a gentle, high-intent nudge.
5. The Dedicated SMS Capture Pop-Up
Trying to collect email and phone numbers simultaneously on step one destroys form conversion rates. We prefer capturing email first, then serving a dedicated SMS capture form down the track to warm subscribers.
To build this, create a segment of profiles who are subscribed to email marketing but not subscribed to SMS. Next, configure a pop-up targeting this exact segment with the following rules:
- Display only on the homepage to avoid interrupting active shopping sessions.
- Set a 30-second delay.
- Set the dismissal behavior so it does not reappear for at least 14 days if closed.
- Ensure compliant SMS disclosure language is cleanly positioned beneath the phone input block.
This allows you to systematically build your SMS database without running aggressive two-step forms on first-time visitors.
Final Thoughts
High list growth is not about blasting every visitor with the same pop-up. By separating your desktop and mobile assets, running PDP-specific flyouts, and serving targeted reminder forms based on purchase history, you create an on-site experience that converts far higher while respecting the customer journey.
Grow Your List with Custom Capture Systems
If you want high-converting, on-brand pop-ups and automated capture flows built and managed for your ecommerce store, explore our Sign-Up Forms service to see how we help brands scale their subscriber base.
