Sticky add-to-cart bar: +45.3% desktop add-to-cart, sales fell
Test run byClean CommitCRO agency
Commentary byLiftArchiveOur analysis, not theirsAdding a sticky add-to-cart bar to product pages raised desktop add-to-cart rate by 45.3%, but overall conversion rate fell 10.6%.
Clean Commit ran this test for an anonymized Shopify store and published it in its A/B test library.
The agency labelled the outcome inconclusive, and we treat it the same way.
- Add-to-cart rate on desktop rose 45.3%: far more shoppers put items in the cart.
- Click-through rate across all devices rose 3.3%, a small lift in engagement.
- Bounce rate on desktop fell 30.2%, so fewer visitors left straight away.
- Conversion rate across all devices fell 10.6%. This is the number that matters most, and it went the wrong way.
- Overall: inconclusive. More carts did not turn into more orders.
The change
The variant adds a sticky add-to-cart bar that follows the shopper down the page.
Simplified mockup drawn by LiftArchive from the shared screenshots.
Control
The product page had no sticky add-to-cart bar. Shoppers had to scroll back up to the main button to add an item.
Variant
A sticky add-to-cart bar stayed on screen as shoppers scrolled. The agency's hypothesis also mentions a size selector with a preselected size inside the bar.
Why it likely came out this way
Our reading of the result, not the practitioner's claim.
- A bar that is always in view makes adding to cart easy, so it pulls in low-intent clicks from shoppers who were not ready to buy.
- If a size is preselected, some shoppers may add the wrong size, then drop out in the cart once they notice.
- The gap between add-to-cart and orders points to friction later in the funnel, which a product page change cannot fix.
- With no sample size or probability shared, part of the swing may simply be noise.
Caveats: No sample size, duration or significance figures were shared. The page title says bottom bar while the hypothesis describes a top bar, so the exact placement is unclear.
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 add a sticky add-to-cart bar to product pages, then more shoppers will complete an order because the button stays within reach as they scroll.
- Primary metric
- Conversion rate (orders per visitor), not add-to-cart rate
- Guardrails
- Cart abandonment rate
- Revenue per visitor
- Return or exchange rate if a size is preselected
- Who should test it
- Stores with long product pages where the main button scrolls far out of view. Be careful with sized products: do not preselect a size, and judge the test on orders, not carts.
Questions
Does a sticky add-to-cart bar increase sales?
Not always. In this test it lifted desktop add-to-cart rate a lot, but overall conversion rate dropped 10.6%. Measure orders, not just carts.
Should a sticky add-to-cart bar preselect a size?
It is risky. Preselecting a size makes adding faster, but shoppers may add the wrong size and abandon later or return the item.
Why can add-to-cart go up while conversion goes down?
An easier button attracts clicks from shoppers who are still browsing.
Many of those carts never reach checkout, so orders do not follow.
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