For a list of products or search results, the short answer is 50-150 items on desktop and 15-30 items on mobile. The number is a range because it varies according to context. Generally, the more information a customer needs to make a purchasing decision, the fewer the number of items you should include in a list.
For electronics like, say, laptops, you should go with fewer items. This is because people need to read the product description and compare specifications before making a decision. For items like clothing, decisions are often made by just looking at the images so you can get away with including more items on a list.
You can also get away with more items on desktop simply because there is more space. The viewport on a desktop can fit 12-16 items so you can fit 50 items without the user scrolling too much. 50 items on mobile would be excessive, however, because the screen can only fit six to eight items.
Why stick to ideal item ranges?
Why not show five products? Or 500? Both are bad ideas. Too few items and a customer might feel like your store doesn’t have enough product diversity. Too many, and the customer is too overwhelmed by decision paralysis to actually buy anything.
15-30 items on mobile and 50-150 on desktop are the sweet spots. They show the customer that you have a wide selection of products without paralyzing them in a state of indecision because there are so many choices to pick from.
Use the “Load More” button instead of pagination and infinite scrolling
First, infinite scrolling is just evil. It’s preferred by social media sites because their goal is to keep users on their sites forever. You, however, don’t have the same luxury.
Facebook makes money the more time a person spends scrolling. You on the other hand, only make money when someone actually buys something. Having infinite scrolling enabled means your would-be customers spend more time scrolling and looking at pictures than they do researching products and adding them to their carts.
There are also many links in your footer that your customers may want to get to. With infinite scrolling, they’ll never get to the footer. So, always avoid infinite scrolling.
Pagination is no good either. The links are too close together and create too much cognitive load. Seeing that there are 27 more pages of results left can be exhausting.
The best way to manage long pages is a combination of lazy loading and the “Load more” button. This allows you to show a customer the full range of what you have to offer without overwhelming them with a sheer number of choices at once, breaking your navigation, or slowing down your site.