How to add a custom popup in Shopify in 2026

A custom Shopify popup in 2026 is usually an app, not a theme hack. Start with Shopify Forms or the forms inside Klaviyo if you already pay for them. StoreCensus (23 August 2026) puts Klaviyo at 274,598 email-app installs and Privy at 37,069. Theme Liquid popups still work, but they skip targeting, A/B tests and a consent record.

Should you use Shopify Forms, your ESP, or a popup app?

Four rungs. Climb only as far as the job.

1. Theme email signup. Online Store 2.0 themes (Dawn and most OS 2.0 themes) have an email signup section. Footer or homepage. No overlay. Fine for a first store.
2. Shopify Forms. Free Shopify app. Popup or inline, delay and some targeting, subscribers land on Shopify customers. No serious exit-intent, no wheel, thin analytics.
3. ESP forms. If you already run Klaviyo, Omnisend or Mailchimp, use their signup forms. You avoid a second subscription and a second script. StoreCensus (23 August 2026) has Klaviyo at 274,598 installs (37.5% of the email category), Shopify Forms at 146,684, Mailchimp at 127,284, Omnisend at 72,494, Privy at 37,069.
4. Dedicated popup app. Privy is best for merchants who want capture and the follow-up email in one tool. OptiMonk is best for gamified and on-site personalisation. Poptin is the cheap exit-intent test. Wisepops is for teams who will use every targeting rule.

Do not install Privy on top of Klaviyo forms "for more popups." Pick one overlay tool.

How do you add a popup app without editing theme code?

Online Store 2.0 is built for app embeds. Prefer that over pasting JavaScript into theme.liquid.

1. In Shopify admin, go to Settings → Apps and sales channels, or Apps → Shopify App Store.
2. Install the app. Review the permissions. A popup app that wants to edit theme files is the old path; an app embed is the 2026 path.
3. Online Store → Themes → Customize → App embeds. Toggle the app on.
4. In the app, create a campaign. Set the trigger (delay 6 to 10 seconds or 30% scroll; not immediate on the homepage).
5. Hide it on checkout. Shopify checkout is not your theme; many apps cannot run there, and should not.
6. Preview on a development theme, then on a phone.

Omnisend's 2025 study of 1.24 billion displays put average email-popup conversion at 2.1%, with a delay of 6 to 10 seconds beating immediate (2.4% vs 1.9%). Use that as the first setting, not a 0-second welcome wall.

Google's intrusive interstitial rule still applies to full-screen promotional overlays on mobile, including Shopify stores that rank in Google.

When is custom Liquid still worth it?

When the "popup" is a theme modal with no targeting: a size guide, a materials table, a store-locator overlay opened from a button. Those belong in a section, with no extra vendor.

When you need a campaign with rules, do not paste 200 lines of jQuery into theme.liquid. You will lose it on the next theme update, you will not have a consent log, and you will fight the app embed of whatever you install later.

Checkout and customer accounts: Shopify's hosted customer accounts are not a theme popup you can restyle. Do not promise a login modal if you have moved to the hosted account flow.

What about speed, apps and consent?

Every popup app is another script. INP is a Core Web Vital at 200ms or under. If the store already runs reviews, upsell, loyalty and chat, a fifth overlay tool is how you fail INP.

Consent: a Shopify cookie banner app and a marketing popup are not the same. EU/UK visitors still need a PECR-style yes before non-essential cookies (ICO). SMS capture in the US needs written consent under 47 CFR 64.1200. Privy and Klaviyo both have SMS fields; the legal copy still has to sit next to the button.

Baymard: 70.22% average cart abandonment. If the popup is a cart saver, put it on cart URLs, not on every product.

Popupsmart has a Shopify integration if you already standardised on it. It is not the default Shopify pick; Privy and the ESP you already pay for are.

For campaign hygiene after it is live, see popup mistakes and how to use popups.