Sticky add-to-cart increases purchases

Long product pages have a problem. The buy button is at the top. The detailed specs, reviews, and comparison info are below. By the time someone scrolls through everything and decides to buy, the button is gone. They have to scroll back up.

A sticky bar at the bottom of the screen with the product name, price, and buy button solves this. The button is always there. The moment they decide, the action is one tap away.

This matters even more on mobile where scrolling back up is tedious and breaks the decision momentum. A user who decides to buy while reading the third review shouldn't have to work to complete that decision.

Keep the sticky bar minimal. Product name, price, and button. Not a full product card. Not multiple options. The sticky bar is a shortcut for people who've already decided, not a replacement for the product page.