How to markup lists

As shortly defined on Wikipedia:

A list is any enumeration of a set of items.

I would add to this definition the fact that items within a list must be of the same nature. It helps choosing if a list should be used to markup content. Indeed, if the content contains a set of items of the same nature, ordered or not, it's probably a good situation to use a list.

HTML lists

There are 3 types of list in HTML, each having its different use cases and a different meaning.

Unordered lists

Probably the most used list element rendered as a bulleted list by default (can be changed with CSS). Children order have no importance here. To insure a valid HTML, it's important that each direct child is contained within a list item (<li> element).

<p>Rings of power</p>
<ul>
    <li>3 for the Elves</li>
    <li>7 for the Dwarves</li>
    <li>9 for the Men</li>
    <li>1 for Sauron</li>
</ul>

Ordered lists

As opposed to the previous one, this type of list (<ol> element on MDN) is rendered as a numbered list. The order is meaningful for the list and its children. As for the <ul>, direct children must be <li>. Here is how to markup an ordered list:

<p>The Lord of the Rings movies</p>
<ol>
    <li>The fellowship of the ring</li>
    <li>The two towers</li>
    <li>The return of the king</li>
</ol>

To know if it's better to use a <ul> or <ol> element, try swaping the order of the children: if it's still makes sense, it should probably be an <ul>. Otherwise, it's an <ol>.

Description lists

Lists can have both a title and a description. That's why the <dl> (description list element on MDN) element exists but its usage differs from <ul> and <ol> elements. It if often used for definitions list. Each list item is composed of:

<p>Hobbits</p>
<dl>
    <dt>Frodo</dt>
    <dd>The one ring wearer.</dd>

    <dt>Sam</dt>
    <dd>Definitely the true hero.</dd>

    <dt>Pippin</dt>
    <dd>Clumsy but lovely guy.</dd>
</dl>

As for many HTML elements, you can nest lists as much as you want (until you got a headache figuring which item belongs to which list!). The nested list is part of one list item of the parent list, like in this example:

<p>Middle Earth movies:</p>
<ul>
    <li>
        The Lord of the Rings
        <ul>
            <li>The Fellowship of the Ring</li>
            <li>The Two Towers</li>
            <li>The Return of the King</li>
        </ul>
    </li>
    <li>
        The Hobbit
        <ul>
            <li>An Unexpected Journey</li>
            <li>The Desolation of Smaug</li>
            <li>The Battle of the Five Armies</li>
        </ul>
    </li>
</ul>

In the above example, each sub list is wrapped inside the main list items.

Lists attributes

What we've seen before is the basic knowledge about HTML lists. But they allow us to go further by providing useful attributes. For each following attribute, let's consider an ordered list of 4 items (1, 2, 3, 4).

⚠️ As stated on MDN, while there is a type attribute, it is not recommended to use it. Use the CSS list-style-type property instead.

Common use cases

"When should I use a list?" we could ask. On almost every website, there are use many cases. Here are some common patterns and content we could easily identify:

One thing to check: Is there any repeated content of the same nature that would be appropriately encapsulated within a list?

Thanks for reading!