:focus-within style is applied to the parent element when the focus is obtained or any of its descendants is obtained; 1. Can be used to highlight the form container when the input box is obtained; 2. Can be used to expand the pull-down menu when the button or link is obtained; 3. Can enhance the accessibility of complex controls such as combo boxes to provide visual feedback; be careful not to support IE and only take effect if the element is focused or has a tabindex.
The :focus-within
pseudo-class in CSS is a powerful tool for styling an element when it or any of its descendants receive focus. It's especially useful for enhancing accessibility and user experience in interactive components like forms, dropdowns, or navigation menus.

Here's how to use it effectively:
What :focus-within
does
:focus-within
applications styles to a parent element when it itself or any of its child elements are focused. This is different from :focus
, which only applies to the element that currently has focus.

For example:
.container:focus-within { background-color: #f0f8ff; border: 2px solid #0066cc; }
This rule will apply the background and border to .container
as soon as any input or focusable element inside it gets focus.

Practical use cases
1. Styling form containers on input focus
This helps users identify which form they're interacting with, especially in complex layouts.
<div class="form-group"> <label for="email">Email:</label> <input type="email" id="email" name="email"> </div>
.form-group { padding: 10px; border: 1px solid #ccc; border-radius: 4px; transition: border-color 0.3s; } .form-group:focus-within { border-color: #0066cc; background-color: #f9f9f9; }
Now, when a user clicks into the input, the entire .form-group
container gets highlighted.
2. Dropdown or menu activation
You can use :focus-within
to show a dropdown when a focusable item inside it receives focus—great for accessible menus.
<nav class="dropdown"> <button>Menu</button> <ul> <li><a href="#home">Home</a></li> <li><a href="#about">About</a></li> <li><a href="#contact">Contact</a></li> </ul> </nav>
.dropdown ul { display: none; } .dropdown:focus-within ul { display: block; }
Now, when the button or any of the links get keyboard focus, the menu appears.
3. Enhancing accessibility in complex widgets
For custom widgets like comboboxes or modal dialogs, :focus-within
helps indicate active regions.
.combobox { border: 1px solid #ddd; padding: 8px; } .combobox:focus-within { box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.3); border-color: #0066cc; }
This provides a clear visual cue when navigating via keyboard.
Key points to remember
- Works on any container element (div, form, nav, etc.)
- Triggers when:
- The element itself is focused and focused
- Any descendant is focused (eg, inputs, buttons, links,
tabindex
elements)
- Great for keyboard navigation and accessibility
- Supported in all modern browsers (including Edge, Chrome, Firefox, Safari — not in IE)
Limitations and fallbacks
- No support in Internet Explorer — if IE support is required, you'll need JavaScript to simulate the behavior.
- Doesn't work with non-focusable elements unless they have
tabindex
attributes.
Example with tabindex
:
<div class="box" tabindex="0"> <span>Click me to focus</span> </div>
Now .box:focus-within
will trigger when the div is focused.
Basically, :focus-within
reduces the need for JavaScript in many interactive patterns and makes your CSS more dynamic and user-friendly. It's a small addition that can significantly improve UX with minimal code.
The above is the detailed content of How to use the CSS :focus-within pseudo-class?. For more information, please follow other related articles on the PHP Chinese website!

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