Sticky mobile add-to-cart button: +6.5% conversion, inconclusive
Test run byClean CommitCRO agency
Commentary byLiftArchiveOur analysis, not theirsMaking the add-to-cart button sticky on mobile product pages showed a 6.5% conversion rate lift, but it was not statistically significant, so we treat the result as inconclusive.
Clean Commit ran this test for an anonymized Shopify store and published it in its A/B test library.
Add-to-cart rate, the metric the test targeted, was flat.
- Conversion rate: +6.5% and orders +6.0%, but not significant after 17 days.
- Revenue per visitor: +9.3%, also not significant, helped by a 2.6% rise in order value.
- Add-to-cart rate: -0.5%, flat, with a 46.9% probability of beating the original.
The change
The variant keeps the add-to-cart button on screen while scrolling.
Simplified mockup drawn by LiftArchive from the shared screenshots.
Control
On mobile, the add-to-cart button appeared only in one section of the product page and scrolled out of view.
Variant
The add-to-cart button stayed on screen as shoppers scrolled the whole product page.
Why it likely came out this way
Our reading of the result, not the practitioner's claim.
- A button that is always in view may help shoppers who have already decided to buy, which fits more orders without more adds.
- Shoppers who were going to add to cart anyway did so at the same rate, so the button didn't create new intent.
- With about 10,750 mobile visitors, the test may have been too small to separate a real lift from noise.
Caveats: Not statistically significant: 10,753 mobile visitors over 17 days, and add-to-cart had a 46.9% probability of beating the original. The conversion lift is a signal, not proof.
Who ran it
Clean Commit ran this test for a Shopify store (anonymized) and published the results (Clean Commit A/B test library). The numbers are theirs; the summary and commentary on this page are ours.
Read the original case study on Clean Commit →
How to run this test on your store
- Hypothesis
- If we keep the add-to-cart button on screen on mobile, then more shoppers will add to cart because they won't scroll back to find it.
- Primary metric
- Mobile conversion rate
- Guardrails
- Add-to-cart rate
- Revenue per visitor
- Average order value
- Who should test it
- Stores with long mobile product pages where the buy button scrolls away. Plan for enough traffic to reach significance; small stores may only get a signal.
Questions
Do sticky add-to-cart buttons work on mobile?
Often they help, but results vary. Here conversion rose 6.5% without reaching significance, so it's a signal worth retesting.
Why would orders rise if add-to-cart rate didn't?
The same share of shoppers added items, but more of them finished buying. The test can't say why with confidence.
How much traffic do I need for a sticky button test?
It depends on your baseline rate and the lift you expect.
About 10,750 visitors over 17 days was not enough here.
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