Stop Using Responsive All-in-One Pop-Ups
Most ecommerce brands set up a single sign-up form in Klaviyo, tick the box for both desktop and mobile, and call it a day. That is a mistake.
When you run a combined form, you blind yourself to device-level performance. Desktop visitors browse differently, read differently, and convert under different conditions than someone scrolling on a mobile phone.
For one of our clients, the desktop pop-up converted at 4.4% while the mobile version hit 6.3%. If those two experiences were mashed together into one form, we would have no clear way to test and optimise either of them properly.
Why Mobile and Desktop Forms Need to Be Split
The solution is simple: clone your sign-up form and set one to display only on desktop and the other to display only on mobile. This gives you clean data and lets you run independent A/B tests on each device type.
You might find an immediate pop-up performs best on mobile where attention spans are tiny, while an 8-second delay wins on desktop where visitors are browsing broader product categories. If you keep both devices in a single form, you cannot test those timing variations accurately.
Here is what you should split test across separate device forms:
- Display timing: immediate trigger versus a 5 to 10 second delay.
- Visual layout: side-by-side imagery on desktop versus compact, text-first layouts on mobile.
- Input fields: single-step email collection versus two-step phone capture.
The Untapped Power of Secondary Pop-Up Forms
Getting the subscriber onto your list with a 10% discount is only step one. The real revenue leak happens when someone opts in, browses for two minutes, and leaves without buying.
Most brands rely solely on their automated welcome flows to drag those people back. That works to an extent, but you can also use Klaviyo on-site forms dynamically to remind returning non-buyers about the offer they never redeemed.
We set up secondary pop-up forms that display exclusively to existing subscribers who have never placed an order. It is an on-site safety net that captures high-intent traffic without cluttering the experience for genuine first-time visitors.
Building the Non-Buyer Reminder Segment
To pull this off without annoying your list, you need a dynamic Klaviyo segment with precise criteria. You do not want new subscribers seeing this secondary pop-up five minutes after they joined.
In my books, the ideal segment conditions look like this:
- List membership: Subscribed to your main newsletter list at least once overall time.
- Order history: Placed order equals zero times overall time.
- Recency buffer: Subscribed to list zero times in the last 5 days.
That 5-day buffer is critical. It gives your core welcome series flow time to do its job first, ensuring you do not bombard people with competing messages right after they hand over their email.
Display Rules and Page Targeting Settings
Once your segment is built, you need to configure the form targeting inside Klaviyo so it acts as a helpful reminder rather than an intrusive nuisance.
Set the secondary form to show after 5 seconds on page. Crucially, add a URL exclusion rule so the form never triggers on URLs containing /cart or /checkout. The last thing you want is a pop-up interrupting someone who is already in the middle of typing their shipping details.
Set the frequency cap to display again only after 15 days once dismissed. If someone closes the banner, respect their choice and let them browse in peace.
Final Thoughts
Sign-up forms are not just top-of-funnel list building tools. When you segment them properly, they become high-converting on-site sales drivers that reinforce your email flows.
Split your forms by device first, measure the difference in submission rates, and then build dynamic secondary pop-ups for unengaged subscribers. The extra revenue is sitting right there.
Work With In-box
If you want high-converting pop-up strategies and custom Klaviyo forms built for your store, take a look at our Sign-up Forms service to see how we help ecommerce brands grow their lists and revenue.
