Mobile sticky add-to-cart: +6.8% adds, -7.7% conversion rate
Test run byClean CommitCRO agency
Commentary byLiftArchiveOur analysis, not theirsPinning the add-to-cart button to the bottom of the mobile screen raised add-to-cart rate by 6.8% but lowered conversion rate by 7.7%, an inconclusive result.
Clean Commit ran this test for an anonymized Shopify store and published it in its A/B test library.
On the target metric, the variant had only a 50.6% probability of beating the original.
- Add-to-cart rate: +6.8%, the target metric, but only a 50.6% probability of beating the original. Inconclusive.
- Conversion rate: -7.7%, a negative but not significant result.
- Revenue per visitor: -22.1%, as average order value fell 15.5%.
- Orders: -6.1%.
The change
A sticky add-to-cart bar stays at the bottom of the mobile screen.
Simplified mockup drawn by LiftArchive from the shared screenshots.
Control
On mobile, the add-to-cart button sat in its fixed section of the product page.
Variant
The add-to-cart button stayed fixed at the bottom of the mobile screen as shoppers scrolled.
Why it likely came out this way
Our reading of the result, not the practitioner's claim.
- An always-visible button makes adding easy, but does not answer the questions that lead to buying.
- Easier adds may bring in shoppers who were less sure, who then drop off before checkout.
- The order value drop may be noise in a small sample rather than an effect of the button.
Caveats: 7,948 mobile visitors over 15 days, and no metric reached significance. Metrics moved in opposite directions.
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 make the add-to-cart button sticky at the bottom of mobile product pages, then add-to-cart rate will rise because shoppers don't have to scroll back to find it.
- Primary metric
- Add-to-cart rate on mobile
- Guardrails
- Conversion rate
- Revenue per visitor
- Average order value
- Who should test it
- Stores with long mobile product pages where the buy button scrolls out of view. If your page is short, a sticky button adds little. Judge it on orders, not just adds.
Questions
Does a sticky add-to-cart button increase sales on mobile?
Not clearly. In this test, adds rose 6.8% but conversion rate fell 7.7%, and neither result was significant.
What should I measure when testing a sticky add-to-cart?
Track conversion rate and revenue per visitor, not only add-to-cart. Here the two moved in opposite directions.
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