A popup is the only element on a store designed to interrupt. Done badly it costs you the session you paid for; done well it is the cheapest way to build an audience you own rather than rent from an ad platform. The apps below are close enough in features that the decision is rarely about the tool — it is about when the thing appears, what it offers, and whether the address it captures ever gets used.
Summary
- Shopify Forms — free, native, clean customer records. Start here.
- Klaviyo — if your flows are already in Klaviyo, its forms are the least friction.
- Privy — popups with email and SMS built in, for stores without a full ESP.
- OptiMonk — the targeting and testing platform for teams that will actually use it.
1. Shopify Forms (free)
Shopify Forms is Shopify’s own: email and SMS capture in popups, banners and inline forms, with basic display rules, and the captured contact landing directly in your Shopify customer list with marketing consent recorded properly. It also handles wholesale and lead forms.
For most stores this is the right first install: no extra script vendor, no consent mismatch between the popup and the customer record, and nothing to pay. Its limits are targeting depth and testing — there is no multi-step offer builder and no serious experimentation.
2. Klaviyo’s own forms
If you already run Klaviyo, its forms are the path of least resistance: the subscriber lands in the list and the welcome flow with no sync step, targeting uses Klaviyo’s own profile data (has purchased, is in this segment, viewed this collection), and the reporting sits beside the flow that receives the address. The same is true of Attentive and Postscript for SMS-first brands — see the retention apps comparison.
3. Privy
Privy bundles popups with email and SMS sending, which suits stores that want list-building and basic campaigns without committing to a full retention platform. Templates are quick, the display rules cover the common cases, and there is a free tier to start.
4. OptiMonk
OptiMonk is the specialist: granular targeting (traffic source, cart contents, returning versus new, geography), multi-step and gamified popups, personalised messages tied to what the visitor browsed, AI-assisted building, and proper A/B testing of variants. It is the right pick when someone owns the programme and will iterate on it; installed and forgotten, it is an expensive version of the free app.
Quick comparison
| App | SMS | Targeting | A/B testing | Price | Best for | |
|---|---|---|---|---|---|---|
| Shopify Forms | Yes | Yes | Basic | No | Free | Most stores, first install |
| Klaviyo forms | Yes | Yes | Profile and segment based | Yes | Included with Klaviyo | Stores already on Klaviyo |
| Privy | Yes, with sending | Yes | Moderate | Basic | Free tier, then tiered | List-building without a full ESP |
| OptiMonk | Yes | Via integration | Deep | Yes | Tiered | Teams running a real programme |
The rules that decide whether it works
- Never before the first paint. A popup over a homepage the visitor has not seen is the fastest way to lose them. Trigger on exit intent, a second page view, or 25–50% scroll.
- One popup, one job. An email capture and a shipping banner and a cookie notice and a chat bubble is four interruptions. Stack them in order of value and drop the rest.
- Offer something you would want. On a premium brand, early access, a restock alert, a fit guide or a genuinely useful guide beats a discount — and does not train the customer to wait for a code. When a discount is the offer, make it single-use and time-boxed.
- Ask for what you will use. Email if you send email. SMS only if SMS is a channel you run, with explicit consent language; an unused SMS list is a compliance liability, not an asset.
- Mobile gets its own design. Half-screen sheets, a 44px close button, and never a full-screen takeover that traps a scroll.
- Respect the answer. Dismissed means gone for at least a week, and a customer who subscribed should never see it again.
- Measure the session, not the signup. A popup with a 6% signup rate that drops conversion 4% is a loss. Compare sessions that saw it with those that did not.
What to do with the address
The capture is the easy half. The value is in the welcome sequence, the browse and cart flows behind it, and the replenishment timing that brings the customer back — which is the programme described in our retention marketing work and measured on the repeat purchase rate, not on list size. A list that receives one campaign a quarter is a cost.
The same applies to seasonal capture: our own BFCM readiness work treats the popup as the front of a funnel that has to be built before the traffic arrives, not a switch flipped in November.
The speed cost
Every popup app loads a script on every page, and some load fonts and an iframe with it. Shopify Forms is the lightest because it is native; the platforms cost more. Measure with the free Store Speed Test before and after installing, and keep one popup vendor — two is a common finding in audits, usually because a previous agency left one behind. The speed apps guide covers what else is loading ahead of your first image.
FAQ
Do popups hurt conversion?
A popup that appears before the visitor has seen anything does. One that appears on exit intent, on a second page view, or after 25% scroll generally does not, and it is one of the cheapest ways to build a list you own. Measure conversion rate for sessions that saw the popup against those that did not.
Is Shopify Forms enough?
For a straightforward email or SMS capture with basic rules, yes, and it is free and native with clean Shopify customer records. Privy and OptiMonk earn their fee on targeting, A/B testing, multi-step offers and personalised content.
Should I capture SMS as well as email?
Only if you will use it. SMS consent has its own compliance rules and a cost per message, so an unused SMS list is a liability. If SMS is a channel you actually run — Attentive or Postscript — capture it in the same flow with explicit consent language.
What discount should a popup offer?
On a premium brand, often none: early access, a size guide, a restock alert or a genuinely useful guide converts better and does not train customers to wait for a code. When a discount is the offer, make it single-use and time-boxed.
