Introduction
The <dl>, or description list, element is underrated.
It’s used to represent a list of name–value pairs. This is a common UI pattern that, at the same time, is incredibly versatile. For instance, you’ve probably seen these layouts out in the wild…
Each of these examples shows a list (or lists!) of name–value pairs. You might have also seen lists of name–value pairs to describe lodging amenities, or to list out individual charges in your monthly rent, or in glossaries of technical terms. Each of these is a candidate to be represented with the <dl> element.
So what does that look like?
The Anatomy of a Description List
I’ve been saying “<dl>,” when really, I’m talking about three separate elements: <dl>, <dt>, and <dd>.
We start with our <dl>. This is the description list, akin to using a <ul> for an unordered list or an <ol> for an ordered list.
<dl>
</dl>Fancy.
Next up, we want to add a name–value pair. We’ll use a <dt>, short for description term, for the name, and we’ll use a <dd>, short for description detail, for the value.
<dl>
<dt>Title</dt>
<dd>Designing with Web Standards</dd>
</dl>To add another name–value pair to our list, we add another <dt> and <dd>:
<dl>
<dt>Title</dt>
<dd>Designing with Web Standards</dd>
<dt>Publisher</dt>
<dd>New Riders Pub; 3rd edition (October 19, 2009)</dd>
</dl>But wait — what if I have a term that has multiple values? For instance, what if this book has multiple authors?
That’s fine! One <dt> can have multiple <dd>s:
<dl>
<dt>Title</dt>
<dd>Designing with Web Standards</dd>
<dt>Author</dt>
<dd>Jeffrey Zeldman</dd>
<dd>Ethan Marcotte</dd>
<dt>Publisher</dt>
<dd>New Riders Pub; 3rd edition (October 19, 2009)</dd>
</dl>There’s one last piece of the description list anatomy to look at for most basic use cases: what if I want to wrap a <dt> and its <dd>(s) for styling reasons?
In this case, the specs allow you to wrap a <dt> and its <dd>(s) in a <div>:
<dl>
<div>
<dt>Title</dt>
<dd>Designing with Web Standards</dd>
</div>
<div>
<dt>Author</dt>
<dd>Jeffrey Zeldman</dd>
<dd>Ethan Marcotte</dd>
</div>
<div>
<dt>Publisher</dt>
<dd>New Riders Pub; 3rd edition (October 19, 2009)</dd>
</div>
</dl>A wrapper <div> like this is the only element that can wrap those <dt>/<dd> groups.
And that’s it! That’s the anatomy of the description list, HTML's semantic way to mark up a list of name–value groups!
Why Do We Need Semantics For This Anyways?
Before we learned about the <dl>, <dt>, and <dd> elements, my team used to use nested <div>s for this pattern all the time. It looked a lot like:
<div class="book-details">
<div class="book-details--item">
<div class="book-details--label">
Title
</div>
<div class="book-details--value">
Designing with Web Standards
</div>
</div>
<div class="book-details--item">
<div class="book-details--label">
Author
</div>
<div class="book-details--value">
Jeffrey Zeldman
</div>
<div class="book-details--value">
Ethan Marcotte
</div>
</div>
<div class="book-details--item">
<div class="book-details--label">
Publisher
</div>
<div class="book-details--value">
New Riders Pub; 3rd edition (October 19, 2009)
</div>
</div>
</div>This has all the information about the book, right? Why do we need semantics for a list of name–value groups in the first place if something like a series of nested <div>s could get the job done?
When determining whether a semantic element might be appropriate for a given pattern, I find it helpful to ask, “What benefits — even theoretical — could we get if computers could recognize this pattern?” In this case, what lift could we get if browsers could somehow recognize a list of name–value groups?
Answers to that question will be varied. I tend to spend a lot of time advocating for web accessibility, so my first thought tends to be how screenreaders could interpret the pattern. Off the top of my head, I can think of a couple of benefits screenreader users could get from their screenreaders recognizing this pattern:
- The screenreader could tell the user how many name–value groups are in the list.
- The screenreader could tell the user how far into the list they are.
- The screenreader could treat the list as one block that the user could skip over if they’re uninterested in it.
All of these could make the list more usable than a series of nested <div>s, which would treat each name and value in the list as nothing more than a standalone text node.
If you can come up with a couple of even theoretical lifts from the user’s device recognizing a pattern, then there’s a good chance that the pattern is a strong candidate for having some associated semantics.
For what it’s worth, these screenreader experiences aren’t hypothetical — they’re benefits that screenreader users really get from using <dl> in most browser/screenreader combinations. Admittedly, however, support for the <dl> element is not yet universal. You may decide that screenreaders’ fallback experience — treating the list as standalone text nodes — isn’t sufficient for your use case, and instead opt for something like a <ul> until support improves.
Okay, Okay, One Last Example!
My favorite example, the one that really takes the cake for me, is Dungeons & Dragons statblocks, which are really “Oops! All Name–Value Pairs!”
No, really: just how many candidates for <dl>s do you see in this statblock alone?
I counted five possible description lists, personally. Here’s how I chose to mark this up:
<div>
<h1>Kobold</h1>
<small>Small humanoid (kobold), lawful evil</small>
<dl>
<div>
<dt>Armor Class</dt>
<dd>12</dd>
</div>
<div>
<dt>Hit Points</dt>
<dd>5 (2d6 - 2)</dd>
</div>
<div>
<dt>Speed</dt>
<dd>30 ft.</dd>
</div>
</dl>
<dl aria-label="Ability Scores">
<div>
<dt>STR</dt>
<dd>7 (-2)</dd>
</div>
<div>
<dt>DEX</dt>
<dd>15 (+2)</dd>
</div>
<div>
<dt>CON</dt>
<dd>9 (-1)</dd>
</div>
<div>
<dt>INT</dt>
<dd>8 (-1)</dd>
</div>
<div>
<dt>WIS</dt>
<dd>7 (-2)</dd>
</div>
<div>
<dt>CHA</dt>
<dd>8 (–1)</dd>
</div>
</dl>
<dl aria-label="Proficiencies">
<div>
<dt>Senses</dt>
<dd>Darkvision 60 ft.</dd>
<dd>Passive Perception 8</dd>
</div>
<div>
<dt>Languages</dt>
<dd>Common</dd>
<dd>Draconic</dd>
</div>
<div>
<dt>Challenge</dt>
<dd>1/8 (25 XP)</dd>
</div>
</dl>
<dl aria-label="Traits">
<div>
<dt>Sunlight Sensitivity</dt>
<dd>
While in sunlight, the kobold has disadvantage
on attack rolls, as well as on Wisdom (Perception)
checks that rely on sight.
</dd>
</div>
<div>
<dt>Pack Tactics</dt>
<dd>
The kobold has advantage on an attack roll against
a creature if at least one of the kobold's allies
is within 5 ft. of the creature and the ally
isn't incapacitated.
</dd>
</div>
</dl>
<h2 id="actions">Actions</h2>
<dl aria-labelledby="actions">
<div>
<dt>Dagger</dt>
<dd>
<i>Melee Weapon Attack:</i> +4 to hit, reach 5 ft.,
one target. <i>Hit:</i> (1d4 + 2) piercing damage.
</dd>
</div>
<div>
<dt>Sling</dt>
<dd>
<i>Ranged Weapon Attack:</i> +4 to hit, reach 30/120 ft.,
one target. <i>Hit</i>: (1d4 + 2) bludgeoning damage.
</dd>
</div>
</dl>
</div>This is just one way you could have opted to mark up that statblock.
I love this as a demonstration because it really goes to show just how versatile the description list pattern can really be — the lists of ability scores (STR, DEX, and so forth) and attacks both look very different, and yet, the description list pattern can span them all.
Takeaways
Lists of name–value pairs (or, in some cases, name–value groups) are a common pattern across the web, in part due to their versatility. HTML lets us mark up these lists with a combination of three elements:
- The
<dl>, or description list, element, which wraps the entire list of name–value pairs - The
<dt>, or description term, element, which represents a name in our name–value pairs - The
<dd>, or description detail, element, which represents a value in our name–value pairs
Ascribing semantics to patterns such as these gives our users’ devices the information they need to curate useful, usable experiences — oftentimes in ways that we as developers may not expect.
To learn more about description lists and what’s allowed or not allowed, I recommend the MDN docs on the <dl>, or going directly to the specs!
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` 内部可放置元素的限制。用户们了解到，HTML 标准通常建议使用 `` 元素作为 `- `（术语）和 `
- `（描述）组的包裹容器，以保持语义的有效性，对此感到很有趣。
对话还涉及了使用该元素所面临的实际挑战，尤其是其在屏幕阅读器和可访问性方面历史性的不一致表现。尽管一些开发者认为使用 `
` 在语义准确性上令人满足，但其他人仍对其布局限制和跨浏览器支持持谨慎态度，引发了关于“语义纯粹性”与灵活实用编码实践之间平衡的讨论。