Sticky add to cart with swatches and bottom placement: inconclusive
Test run byBlend CommerceCRO agency
Commentary byLiftArchiveOur analysis, not theirsAdding colour swatches to the desktop sticky add-to-cart bar and moving the mobile sticky button to the bottom of the screen lifted conversion rate by 7% for Little Bible Stories, but we count the result as inconclusive.
Blend Commerce ran this A/B/C test on product pages, and the gain was not statistically significant.
Revenue per visitor stayed flat and fell 18% on mobile.
- Conversion rate: +7%, but not statistically significant.
- Add-to-cart rate: +8%, and sticky add-to-cart clicks: +27%.
- Revenue per visitor: flat overall, so more orders did not mean more revenue.
- Mobile revenue per visitor: -18%. Desktop conversion: -5%, despite 148% more sticky clicks. Device splits were not significant either.
The change
Sticky add to cart gets colour swatches and a bottom-of-screen mobile position.
Simplified mockup drawn by LiftArchive from the shared screenshots.
Control
The existing sticky add-to-cart used a text dropdown for colour on desktop and only became useful on mobile after shoppers scrolled through the product content.
Variant
Variant 2 showed visual colour swatches in the desktop sticky bar and pinned the mobile sticky button to the bottom of the screen. A third arm (Variant 1) used the same swatches but put the mobile button at the top.
Why it likely came out this way
Our reading of the result, not the practitioner's claim.
- Swatches show options at a glance, so more shoppers clicked the sticky bar. That did not carry through to revenue.
- A bottom-of-screen button is easier to reach with one thumb, which may explain the mobile engagement gain.
- Mixed results across devices and flat revenue suggest the changes moved clicks more than purchases. The agency planned a follow-up test on the mobile revenue drop.
Caveats: This was an A/B/C test, and neither the overall nor the device-level results were statistically significant, so we treat it as inconclusive. The agency still rolled out Variant 2. Sample size and test length were not shared.
Who ran it
Blend Commerce ran this test for Little Bible Stories and published the results (Blend Commerce A/B test). The numbers are theirs; the summary and commentary on this page are ours.
Read the original case study on Blend Commerce →
How to run this test on your store
- Hypothesis
- If we show visual swatches in the sticky add-to-cart bar and pin it to the bottom of the mobile screen, then more shoppers will add to cart and buy because options are clearer and the button is easier to reach.
- Primary metric
- Conversion rate
- Guardrails
- Revenue per visitor, split by device
- Average order value
- Add-to-cart rate
- Who should test it
- Stores with products in several colours or styles that already use a sticky add-to-cart. Plan for enough traffic to reach significance per device; small stores may struggle to get a clear answer from a three-way test.
Questions
Should a sticky add-to-cart button sit at the top or bottom on mobile?
In this test the bottom position did better than the top, likely because it is easier to tap with one thumb. The results were not statistically significant, though.
Do colour swatches beat dropdowns?
Swatches drew more clicks here, but sales gains were not significant and desktop conversion fell. Test them against your own revenue numbers.
Why can conversion rise while revenue per visitor stays flat?
More, smaller orders can cancel out. Always check revenue, not just conversion, before you call a winner.
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