# Overview

A theme test compares your entire live Shopify theme against a different version of that theme. Unlike a (which tests a single template), a theme test swaps everything: the header, footer, global styles, fonts, colors, cart type, and every template in the theme.

### How theme tests work

When you run a theme test, Shoplift splits your traffic between two themes:

* **Control**: your current live (published) theme. This is what visitors normally see.
* **Variant**: a separate, unpublished theme. Shoplift redirects visitor to a preview of this theme for visitors assigned to the variant group.

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**FAQ: Will my website visitors see the theme preview bar?**

No. Shoplift hides the theme preview bar for all website visitors participating in a theme test, for as long as the theme test is active. When the theme test ends, Shoplift will return any visitors on the preview theme to the live theme.
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Once a visitor is assigned to the variant, they see the variant theme on every page for the duration of the test. Return visitors continue seeing the same theme they were originally assigned to.

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Theme tests require a brief page redirect for variant visitors on their first page load. Shoplift's anti-flicker system prevents the control theme from being visible during this redirect, so the experience feels seamless.
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### When to use a theme test

Use a theme test when the change you want to test affects elements that are shared across your entire store, not just a single page type. Some common examples:

* **Header and navigation design**: Test a new header layout, a sticky nav bar, or a different menu structure
* **Footer content**: Test adding trust badges, changing link layout, or adding a newsletter signup
* **Announcement bar**: Test different messaging, styling, or whether to show one at all
* **Global styling**: Test new brand colors, fonts, spacing, or a visual refresh across the whole store
* **Cart experience**: Test a drawer cart vs. a dedicated cart page
* **Sitewide layout changes**: Test a new page width, section spacing, or design system

#### Theme test vs. template test

If your change only affects one page type (like the product page or homepage), use a template test instead.

Use a theme test when:

* Your change involves the header, footer, or announcement bar (these are section groups shared across all pages)
* You're changing global theme settings like colors, fonts, or cart type
* You're testing changes across multiple page types at once
* You want to test a completely different theme design

Use a template test when:

* Your change is limited to a single page type (product pages, collection pages, homepage, etc.)
* You're testing section-level changes like reordering content or adding a new block

### What theme tests can change

Because a theme test swaps the entire theme, it can change anything that lives within the theme:

* Header and footer layout, content, and styling
* Announcement bar text, design, and visibility
* Global colors, fonts, and spacing
* Cart type (page cart vs. drawer cart)
* All template files and their configurations
* Custom Liquid, CSS, and JavaScript

### What theme tests cannot change

Theme tests swap the *theme*, not the *store*. Anything stored at the store level stays the same across both themes:

* **Product data**: titles, descriptions, images, prices, and variants
* **Collection content**: which products belong to which collections
* **Page and blog content**: the body text of pages and blog posts
* **Checkout configuration**: checkout layout and branding
* **Shipping, payments, and discounts**: these are store-level settings

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Want to test product prices, images, or descriptions? Those are store-level data, not theme-level, so they can't vary between themes. Use a price test for prices or a URL redirect test for other product-level changes.
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#### Other notes

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It is important to end your theme tests in Shoplift prior to deleting any themes. Otherwise, your website visitors may be redirected to the deleted theme, which will present them with an error on your store.
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Creating and deploying page builder pages while a theme test is active will pause your active theme test, since the template is not shared by both original and variant themes. For more information, see [Theme Compatibility](https://docs.shoplift.ai/test/test-compatibility).
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