Why CSS :focus-within is amazing

This is not a :focus selector, which will highlight when you focus on an element. But a selector to fire when something within is focussed.

In our case, we'll be focusing on forms (I see what you did there 😏)

The end result will look like this:

CSS focus-within selector

HTML Structure

As for our HTML, we wil create a form with 2 inputs.

<form>
  <label for="username">Username</label>
  <input type="text" name="username" />
  <br /><br />
   <label for="password">Password</label>
  <input type="password" name="username" />
</form>

That's all we need for this specific demo.

CSS focus-within pseudo selector

The :focus-within is a pseudo-selector, like :before or :after.

Let's first add some basic styling.

body {
  display: flex;
  min-height: 100vh;
  justify-content: center;
  align-items: center;
}
form {
  border: 1px dashed #333;
  padding: 25px;
}

This will make sure our form is absolutely centered on the page and has a small border to showcase our effect later on.

Now we want to draw the users attention to the form, but making it a fancy colour when they focus an input field.

form {
  border: 1px dashed #333;
  padding: 25px;
  transition: background 0.3s ease;
}
form:focus-within {
    background: #f4d35e;
}

This will change the background of our form to yellow.

You can see this in this Codepen.

Making it more awesome

Yes, we can even make it more awesome by using a box-shadow hack we can create a kind of modal effect!

form {
  border: 1px dashed #333;
  padding: 25px;
  transition: all 0.3s ease;
  box-shadow: 0 0 0 100vmax rgba(0, 0, 0, 0);
}
form:focus-within {
  background: #f4d35e;
  box-shadow: 0 0 0 100vmax rgba(0, 0, 0, 0.7);
}

We create a box-shadow that is 100% of the viewport biggest position (width or height). Initially, this will be at 0 opacity.

When we have a :focus-within we change the opacity to 70%.

The effect is a lightbox-like effect ✨.

Browser Support

The :focus-within selector actually has pretty good support, considering IE is dead already.

CSS focus-within selector browser support

Thank you for reading, and let's connect!

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Emily Boston's photo

I have never used :focus-within. It's really interesting. Thank you, Chris, for writing this post.

Chris Bongers's photo

Thanks for your comment Emily, It's also new for me, but looks pretty cool.

Tapas Adhikary's photo

Good, I learned something new with this... Thanks!

Chris Bongers's photo

Awesome! Can't believe I got to teach you something new 😋

Jesper Hasselquist's photo

Really nice article on the :focus-within pseudo-class! Really good use of it! 🥳 I would just like to make a few clarifications, if you don't mind.

::before and ::after are pseudo-elements and not pseudo-selectors. And technically :focus-within is referred to as a pseudo-class. Pseudo-elements should generally be used with double :: to tell them apart from pseudo-classes which should be referred to with a single :. They are all used together in CSS selectors.

Chris Bongers's photo

Hey Jasper, nice addition you are absolutely right on that actually!

Adam's photo

I really appreciate your discovery! Thanks for sharing your knowledge :) I will definitely use it :)

Chris Bongers's photo

Thanks for this comment Adam, Will keep sharing these cool finds with you guys

Stefan Natter's photo

Thanks for making me aware of this. It comes with no surprise to me that IE does not support this. I'll be forever happy when the browser is not used anymore. :D

Chris Bongers's photo

100% Let's hope this browser just disappears for good, not even mentioned in canIuse etc...

Stefan Natter's photo

Yes, imaging looking at all those tables and there is no red column anymore!