Understanding A/B Testing Cookie Retention

A/B Testing Cookie Retention FAQ

Q: What is the cookie retention period when a visitor hits an A/B Test?

A: It depends on the type of test:

Theme Tests

Shopify sets a cookie called _shopify_essential  that locks a visitor into the theme they preview.

Expiry: 1 year from when it’s set.

To exit, a user must either:

• Delete the cookie, or
• Navigate to another theme using a parameter (?preview_theme_id=123 ).

Behavior When Ending Theme Tests

The default behavior when ending Theme Tests is as follows:

• If a customer is browsing on your current published theme and you publish a new theme, the customer will automatically see the newly published theme (this will stop you from collecting any new analytics events on the current test).
• If a customer was assigned to a Variant Theme during a Theme Test and the test ends, they are redirected to your default (published) theme.
• If you later publish a new theme, those customers will automatically see the newly published theme as well.

This ensures customers are no longer persistently locked into outdated variant themes after a test ends.

Note on Previous Workaround

Previously, you needed to duplicate and delete Variant Themes to prevent returning visitors from continuing to see them due to Shopify’s 1-year cookie.

This manual workaround is no longer required when ending Theme Tests.

Split URL, Page, and Template Tests

Variants are cached for the session.

Expiry: 2 hours after inactivity (based on Shopify’s _shopify_s  session cookie).

Analytics Cookies

Our analytics layer sets a session cookie without a fixed expiry.

Expiry: Lasts for the browser session (until the window is closed or cookies are cleared).

Q: Do we use our own cookies for A/B test functionality?

A: No, the A/B test behavior relies entirely on Shopify’s cookies.

Q: Where can I find Shopify’s official cookie policies?

A: Shopify Cookie Policy → See section “Reporting and Analytics.”