> For the complete documentation index, see [llms.txt](https://docs.elevateab.com/elevate-helpcenter/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.elevateab.com/elevate-helpcenter/custom-code-testing/troubleshooting-custom-code-experiments-and-faqs.md).

# Troubleshooting Custom Code Experiments and FAQs

Fixes for common custom code experiment problems in Elevate A/B Testing, plus answers to frequent questions about targeting, control code, and implementing winners.

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### The code does not run at all

**Likely cause.** The theme extension is not enabled, or the page is outside your targeting.

**Fix.** Confirm the extension is on. Then check **Run on all pages** and your **Exclude pathnames**, and confirm the page you are testing is not excluded.

### The code runs on pages it should not

**Likely cause.** **Run on all pages** is on with no excludes, or a wildcard is broader than intended.

**Fix.** Add the paths to **Exclude pathnames**, or turn off **Run on all pages** and specify where the code should run. Remember `/products*` matches every product page.

### The change appears, then disappears

**Likely cause.** Your code runs before the element exists, or the theme rerenders the section afterwards and overwrites your change.

**Fix.** Wait for the element rather than querying at load, or reapply the change when the theme rerenders. Themes that update the page after a variant change are the usual culprit.

### Console errors on the variation

**Likely cause.** Your code assumes an element or a global that is not present on that page.

**Fix.** Guard for the element before using it, and test on every page type your targeting includes, not only the one you built against.

### The variation is slower than the control

**Likely cause.** Heavy DOM work or a large injected script.

**Fix.** Reduce the work the code does on load. A speed difference is a second change and it will affect your result.

### The variation broke something on the theme

**Likely cause.** A CSS override or DOM change collided with theme behavior.

**Fix.** Pause the experiment first, which stops the code immediately, then narrow the selectors and retest in Preview.

### Results look flat and I expected a difference

**Likely cause.** The code may not be running for the visitors you think.

**Fix.** Confirm the targeting covers the pages that matter, and check whether an audience filter narrowed the experiment more than intended.

### FAQs

**Does custom code testing need the theme extension?** Yes. The code is injected into the page, so the extension is required and the experiment cannot launch without it.

**Can my control have code too?** Yes. The **Control** card has its own JavaScript and CSS fields. Leave them empty to compare against your store as it is, or fill them in to compare two implementations.

**How many variations can I run?** Up to five including your control.

**What does my JavaScript have access to?** Your code receives a `context` object describing the experiment. Expand the note under the code fields in the app for what it contains.

**What happens to my code when the experiment ends?** It stops running. Pausing and completing both remove the code from your storefront immediately.

**How do I keep a winning change?** Implement it in your theme. Experiment code is written to run injected on top of a page, so it usually needs adapting rather than pasting as is.

**Which Shopify plans support it?** All of them.

**Can I edit the code while the experiment is running?** You can, but changing what is being tested means your data describes two different experiments. End it and start a new one instead.

### Next steps

* Custom Code Testing Overview
* Create a Custom Code Experiment