Creating a full bleed CSS utility

Piccalilli CSS Utility — Issue #2

Andy Bell

Sometimes you want to break your components out of the constraints that they find themselves in. A common situation where this occurs is when you don’t have much control of the container that it exists in, such as a CMS main content area.

This is even more the case with editing tools such as the WordPress Gutenberg editor, where in theory, you could pull in a component from a design system and utilise it in the main content of your web page. In these situations, it can be pretty darn handy to have a little utility that makes the element 100% of the viewport’s width and still maintain its flow within its parent container.

This is when I normally pull the .full-bleed utility class out of my back pocket.

The .full-bleed utility

It’s small, but hella mighty:

.full-bleed {
width: 100vw;
margin-left: 50%;
transform: translateX(-50%);
}

Here it is in a context where it makes a fancy <aside> and a <figure> element bleed out of their parent container.

See the Pen Piccalilli CSS Utility — Issue#2 — Full bleed utility by Andy Bell (@hankchizljaw) on CodePen.

The .full-bleed utility gives those elements prominence and importantly keeps their semantic place in the page. Just how I like it.


🔥 Pro tip: When working with a utility like .full-bleed, it’s a good idea to add an inner container that has a max-width and auto horizontal margin. For this, I normal create a shared .wrapper component like this:

.wrapper {
max-width: 50rem;
margin-left: auto;
margin-right: auto;
}

Having a container like .wrapper helps to create consistent, centred content.


How the .full-bleed utility works

We set the container to be width: 100vw, which equates to the full viewport width. We couldn’t set it to width: 100% because it would only fill the space of its parent element. The parent element’s width is useful though, because by setting margin-left: 50%, we are telling the component to align its left edge to the center of its parent element, because 50% is half of the parent element’s width.

Finally, we use CSS transforms to translateX(-50%). Because the transform works off the element’s dimensions and not the parent’s dimensions, it’ll pull the element back 50vw, because it’s 100vw wide, thus making it sit perfectly flush with the viewport’s edges.

Wrapping up

Hopefully this short and sweet trick will help you out on your projects. If it does, drop me a tweet, because I’d love to see it!