CSS :focus-within

Using :hover to display additional information or elements is a very useful technique but a big drawback to using the hover pseudo-class is that they are usually not accessibility-friendly. Not everyone uses a mouse and some users have visual impairments, so they rely on screen readers or the keyboard -- two functionality that don't technically hover.

Luckily the CSS spec gives us a gift to pair with :hover: :focus-within. With :focus-within developers can modify styles of elements when an element or its children has keyboard focus!

Consider the following HTML template with default CSS styling:

<ul id="sports">
  <li>
    <label>
      <input type="checkbox" name="sports[]">
      Soccer
      <button class="remove">Remove</button>
    </label>
    <!-- ... -->
  </li>
</ul>

#sports .remove {
  display: none;
}

#sports li:hover .remove {
  display: inline-block;
}

With the code above, hovering over a list item would show the "remove" button. That's great for mouse users but totally useless for keyboard users. Let's fix that using :focus-within:

#sports .remove {
  display: none;
}

#sports li:hover .remove,
#sports li:focus-within .remove {
  display: inline-block;
}

Once focus hits the checkbox, the focus is technically within the list item and thus we can employ :focus-within to show the "remove" button.

Accessibility is something that gets considered last but shouldn't be an afterthought; in a way, :focus-within is a useful ally even when accessibility was an afterthought. Even when considering accessibility up front, :focus-within should be in every developer's toolbox!