Sticky add-to-cart bar with size picker: +7.6% ATC, inconclusive
Test run byClean CommitCRO agency
Commentary byLiftArchiveOur analysis, not theirsAdding a sticky add-to-cart bar with size and color dropdowns to AFTCO's mobile product pages lifted add-to-cart rate 7.6%, but we treat the result as inconclusive.
Clean Commit ran this test for AFTCO and published it in its A/B test library.
Clean Commit labelled it inconclusive too, and revenue fell because average order value dropped.
- Add-to-cart rate: +7.6%, the headline number, but not shown to be significant.
- Conversion rate: +2.1%, a much smaller lift than add-to-cart.
- Average order value: -5.2%, and Clean Commit reported that revenue fell as a result.
- Bounce rate: -8.2% and click-through rate +5.1%, so shoppers engaged more with the page.
The change
The variant adds a sticky add-to-cart bar with size and color dropdowns.
Simplified mockup drawn by LiftArchive from the shared screenshots.
Control
The mobile product page had no sticky add-to-cart bar. Shoppers used the standard size, color and add-to-cart controls on the page.
Variant
A sticky bar stayed on screen with size and color dropdowns, an add-to-cart button and a 'Find my size' link.
Why it likely came out this way
Our reading of the result, not the practitioner's claim.
- Keeping size and color choices in reach saves shoppers from scrolling back up, which likely explains the add-to-cart lift.
- A quick-buy bar may push shoppers to add one item and go, rather than browse more, which fits the lower order value.
- Most of the extra add-to-carts didn't turn into orders, so the lift may be noise or low-intent adds.
Caveats: Clean Commit labelled this test inconclusive and shared no sample size, duration or confidence level. Revenue fell because of lower order value.
Who ran it
Clean Commit ran this test for AFTCO 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 mobile bar with size and color dropdowns, then more shoppers will add to cart because they won't need to scroll back to the options.
- Primary metric
- Mobile conversion rate
- Guardrails
- Average order value
- Revenue per visitor
- Add-to-cart rate
- Who should test it
- Apparel and footwear stores with long mobile product pages and several sizes or colors. If your order value depends on bundles or add-ons shown lower on the page, watch revenue closely.
Questions
Should a sticky add-to-cart bar include size and color pickers?
It can help shoppers add to cart without scrolling up.
In this test add-to-cart rose, but revenue fell, so measure sales, not just adds.
Why can add-to-cart go up while revenue goes down?
Extra adds don't always become orders, and a faster path can mean smaller baskets. Here order value fell 5.2%.
Is a 'Find my size' link worth adding?
This test bundled it with the sticky bar, so its own effect is unknown.
It may help apparel shoppers who are unsure of fit.
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