A typical homepage looks something like this: an array of featured products you’re promoting and then your categories. If a user likes one of the products you’re pushing and buys it, fine. If he doesn’t, he can browse through categories or use the search bar. But what if you only have a few products? Do you need to feature categories at all?

The answer depends on your product range. If your store sells a single product, then you don’t need categories. If you sell five products, you don’t need categories either. You can ignore categories up to around nine or ten unique products. Beyond that, they become necessary.

The entire point of the homepage is to give any visiting customer the full range of your offerings with as little effort from the customer as possible. If you have 20 products and don’t feature your categories, it’s likely that a customer may not scroll all the way down to see everything you offer. That is something categories can help you with. They condense information into a single place.

The seven-item limit is informed by both the limitations of human working memory and average session length. The average human can only keep seven items in his working memory at a time. This average human also spends only 10 to 20 seconds on a web page. Since most of this time is spent looking at the actual information on a page rather than scrolling, you need to give any visitor a full overview of your store in a single window.

This is not to say people don’t stay longer. They do. Some may even browse for hours. But those first ten seconds are crucial. You have to grab a visitor’s attention and clearly show what you have to offer them. Your store is not a mystery customers are trying to solve so don’t make it one.

You can have a different homepage display for returning customers but in the case of new users, showing them your full product range in as short a time as possible is crucial. Nothing does this better than categories. If all your products can’t fit in a single window without the need for scrolling, feature categories first. You can have one or two individual products on the homepage but categories first.