Guide ยท 5 min read
Mobile add to cart UX that actually converts.
Most e-commerce traffic is mobile, but most product pages are still designed desktop-first. Here is what the buy button area needs on a phone.
In short
Good mobile add to cart UX means a sticky add to cart button that stays on screen while scrolling, tap targets of at least 44 by 44 pixels, variant selectors that show the current selection clearly, price and shipping info visible before the button, and no layout shifts that move the button as the page loads.
The five rules
- 01
Keep the button on screen
A sticky add to cart bar follows the shopper through images, specs and reviews, so the next step is never a scroll away.
- 02
Make targets thumb-sized
Buttons and variant swatches should be at least 44 by 44 pixels with space between them, so taps land where intended.
- 03
Show the selection state
The chosen size and color must be unmistakable. Ambiguity here causes wrong orders and returns.
- 04
Put cost clarity before the button
Price, discounts and shipping expectations should be visible before or beside add to cart, not discovered at checkout.
- 05
Stop layout shifts
Reserve space for images and banners so the button does not jump as the page loads. A moving button gets missed taps and lost trust.
Common mistakes
Full-width popups over the buy box
Newsletter modals that cover the product on arrival block the one thing the shopper came to do.
Variant pickers that open tiny dropdowns
Native select menus hide options and selection state. Prefer visible swatches or pills.
Sticky bars that hide the price
A sticky bar without the price forces shoppers to scroll back up to confirm the cost.
Common questions
- Should the sticky bar appear immediately?
- Show it once the shopper scrolls past the main add to cart button. Showing it on arrival competes with the primary layout.
- How do I test my own page?
- Open it on a real phone, not just a resized browser. Try to select a variant and add to cart with one thumb. A UsabilityGo audit also reviews your page screenshot for these issues.