Check 20 / 21 LOW impact In the full checklist
Sticky add-to-cart on mobile scroll
What this check is
A mobile shopper who has scrolled into the reviews or the size chart has to scroll back up to buy. A sticky add-to-cart bar keeps the purchase one tap away for the whole length of the page.
How to implement it
Add a sticky bar that appears after the buy box leaves the viewport, carrying the selected variant, the price and the add-to-cart action. Keep it under the thumb zone, respect the safe area on notched devices, and make sure it never covers the consent banner or the cart drawer.
How to verify it
Scroll the product page on a 390px viewport, confirm the bar appears after the buy box scrolls away, adds the currently selected variant, and does not overlap the footer content on iOS Safari.
All 197 checks, one Google Sheet
This page is the summary. The full checklist carries the priority, the impact score and the tool link for every check — all 197 of them, across 14 categories, as a Google Sheet and CSV with lifetime updates.
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