The SMS Popup That Only Shows to Your Email Subscribers
The cheapest SMS list you will ever build is the email list you already own. Across four brands in our portfolio running a popup that shows only to existing email subscribers who have not opted into SMS, the submit rate is 5.09%. That is roughly four times what the same brands' standard on-site signup popups convert at over the same window.
There is no trick to it. Klaviyo ships a targeting option called "Show to email subscribers only" that does exactly this, and almost nobody turns it on. It is one dropdown.
What it actually converts at
Four brands, 90-day window, letter keys because the numbers matter and the names do not. Every one of these is a live popup asking an existing email subscriber for a phone number.
| Brand | Form views | Submits | Submit rate |
|---|---|---|---|
| Brand A | 7,313 | 289 | 3.95% |
| Brand B | 1,503 | 135 | 8.98% |
| Brand C | 353 | 33 | 9.35% |
| Brand D | 376 | 29 | 7.71% |
| Blended | 9,545 | 486 | 5.09% |
The blended rate sits below three of the four brands because Brand A carries most of the volume. The honest range is 3.95% to 9.35%, and nothing in the data explains where a given brand lands in it. Sample sizes on three of these are small enough that a few dozen submits move the rate a full point, so treat the individual numbers as directional and the blend as the number to plan against.
Why the rate is high
A normal acquisition popup interrupts a stranger. This one interrupts someone who already gave you an email address, already opted into marketing, and came back to the site anyway. You are not asking for trust. You are asking for a second channel from somebody who already granted the first one.
That also means the comparison to a standard popup is not clean, and it is worth saying so plainly. Most of those popups ask for an email rather than a phone number, so some of the gap is the warmer audience and some is just a different ask. The part that is clean: one of these brands runs an all-traffic SMS popup and this email-subscribers-only SMS popup at the same time, on the same site, in the same window. Same ask, same creative approach. The all-traffic version converts at 1.14%. The email-subscribers-only version converts at 3.95%.
Audience, not copy. That is the whole finding.
How to set it up
Klaviyo's own documentation for this recommends cloning rather than building fresh, which is right. You keep the branding and the styles and change four things.
- Clone your existing multi-step form. It needs to be a Smart Opt-in multi-step form or a tap-to-text multi-step form. A single-step email form will not work as a starting point.
- Delete the email step. The people seeing this form already gave you their email. Asking again is friction for no gain.
- Set the phone field to SMS Consent: Single step, Promotional only. This is the setting that makes the submit count as a real SMS opt-in rather than a phone number sitting on a profile you cannot legally text.
- Targeting and Behavior tab, Targeting section, Visitors dropdown, "Show to email subscribers only." That single option restricts the form to email subscribers who have not yet opted into SMS.
One implementation note that is easy to miss: targeting depends on Klaviyo recognising the visitor, which means a cookied browser or a click through from an email. A subscriber browsing in a private window is a stranger as far as the form is concerned, and will not see it. That is a ceiling on volume, not a bug, and it is part of why the view counts above are small relative to a site-wide popup.
The version most brands skip
The popup only fires when somebody visits the site. You can reach the rest of the list directly: send a campaign to your email subscribers with a link straight to the form. It costs one send, the audience is already segmented by definition, and it picks up the subscribers who do not happen to browse during the window you are running the popup.
If you are already collecting an intent question at signup, the same logic applies here. See asking a question in your popup for what to do with the answer once you have it.
When not to run it
If your SMS program is not built yet, do not turn this on. Collecting consent you have no sequence to serve is how you end up with a list that goes cold before you use it, and re-permissioning is harder than permissioning. Get the SMS welcome and abandonment flows live first, then switch the targeting on.
The other case to think about is send cost. Every SMS opt-in you collect is a recurring per-message expense, unlike an email address. A subscriber who was going to buy from an email anyway does not get more valuable because you can also text them. Worth reading alongside what a subscriber is actually worth before you decide how hard to push on this.
Methodology
- Source: Klaviyo form reporting, four active ecommerce accounts in the BS&Co portfolio, trailing 90 days as of September 2026
- Included: live popups targeted with "Show to email subscribers only" that ask for a phone number
- Submit rate: form submits divided by form views, the same definition Klaviyo reports
- Brand A's form launched partway through the window, so its view count covers roughly seven weeks rather than the full ninety. The rate is view-normalized and unaffected
- Brand B's form also carries a survey question, so its rate reflects a slightly different form than the other three
- Anonymization: brands are letter keys only, the same convention as our other benchmark posts
Want us to look at what your popup is leaving on the table? We audit the whole capture path, not just the form.