What counts as a guarantee
This collection covers money-back guarantees, warranty and returns messaging, and trust blocks that include a guarantee.
Most tests did not create a new policy.
They made an existing one visible where the purchase decision happens.
The answer first: win/loss record
19 wins, 0 losses, 0 flat. Dave Diederen ran 11 of them, Oliver Kenyon 3, Kasper Dolk 2, Milos 2 and Peter Christensen 1. Kasper Dolk's 'how you'll feel' timeline (+14% conversion rate) was still being confirmed when reported.
Where guarantees were tested
Under or inside the add-to-cart button
This is where most of the wins sit.
Oliver Kenyon added 60-day guarantee and easy returns blocks under Add to Cart for +5.6% conversion rate across 7,800+ orders (+€63,000/month).
Dave Diederen put the guarantee inside the add-to-cart button for +7.48% conversion rate.
Peter Christensen added Warranty and Security buttons below add to cart and moved product info into accordions, reporting +41.42% conversion rate at 95.64% confidence.
Oliver Kenyon's free shipping and returns bar under Add to Cart added +$75,600/month.
Cart and checkout
Dave Diederen added "30-day money-back guarantee" under the checkout button in the cart for +17% conversion rate and +18% revenue per visitor (+£68,640/month).
Three USPs including the guarantee below the Pay Now button won +9.90% conversion rate.
Oliver Kenyon's dispatch, returns and payment block under the cart drawer checkout button won +23.8% revenue per visitor and +21.9% conversion rate at 99.4% confidence, across 200,000+ visitors in 16 days. It is the best-documented test here.
Homepage
Homepage tests bundled the guarantee with other changes: a banner with problem headline, reviews and guarantee (+17.12% conversion rate) and a trust-focused FAQ on shipping and returns (+1.15% revenue per visitor).
@oliverkenyon
@DaveDiederen@DaveDiederen@DaveDiederen@DaveDiederen
@peterac_Biggest wins and their numbers
- Warranty and security buttons plus accordions (Peter Christensen): +41.42% conversion rate.
- Returns and dispatch block in the cart drawer (Oliver Kenyon): +23.8% revenue per visitor.
- Guarantee line under the checkout button (Dave Diederen): +18% revenue per visitor.
- Prominent 60-day badge below ATC (Dave Diederen): +14.50% conversion rate.
- Guarantee section rewritten with a bold headline (Dave Diederen): +12.71% revenue per visitor.
Tests that lost or were flat
None. With 19 wins and no recorded losses, assume some selection: stores share what worked.
No test here compared guarantee lengths, so there is no evidence yet on 30 versus 60 days.
Design patterns that won
- A short guarantee line directly under, or inside, the add-to-cart button.
- The same line repeated under the cart or checkout button.
- Plain wording: "or your money back", not legal-sounding copy.
- Returns and dispatch details shown, not hidden in the footer.
How to add or change a guarantee on Shopify
Most themes let you add a text or icon block under the buy button in the theme editor.
Cart and checkout placement depends on your cart drawer and plan; see checkout tests and trust badge tests.
How to test it on your store
Hypothesis: shoppers worry about being stuck with the product, so showing our existing guarantee under the add-to-cart button will lift conversion rate.
Use revenue per visitor as the main metric and check the sample size calculator.
Untested ideas worth queuing: Dave Diederen's test of guarantee length (14 vs 30 vs 60 days) against price point, Kasper Dolk's extension from 14 or 30 days to 90, and Dave Diederen's guarantee made specific to the product's main objection.