DEV Community

loading...
Cover image for A Guide to Clipping Paths

A Guide to Clipping Paths

jh3y profile image Jhey Tompkins Originally published at jhey.dev on ・9 min read

Seen a bunch about clip-path recently. And with path values now supported in major browsers, figured it was time to write up a guide.

What's a clip-path?

It does what it says on the tin. It clips the viewable parts of an element to a given path.

/* What shape would this give you? Try walking the coordinates in your head */
.clipped {
  clip-path: polygon(100% 0, 20% 50%, 35% 50%, 0% 100%, 70% 50%, 50% 50%);
}
Enter fullscreen mode Exit fullscreen mode

When to clip-path?

It comes in handy when a combination of overflow, transform, border-radius, and other properties won't cut it. In most cases, we're able to achieve what we want without reaching for it. But, some shapes are tricky without it.

For example, how to make a star shape!

How to clip-path?

This demo will throw you straight in so you can see some of the things we can do with it (Best viewed in its own tab).

You'll notice that each value is using percentages. We could use other sizing units such as px, rem, etc. But, this will vary per design and use case. Using percentages has the benefit of keeping things responsive (More on this later). What are those values relative to? Clip paths work off the same coordinate system that we use with other CSS properties. Think about it the same as using top, right, bottom, and left. Each value or coordinate is relative to the element it's applied to.


With that out of the way, let's dig into the different values and what we can do with them.

Inset

Define an inset rectangle where everything outside is hidden away. But, this is a little misleading. It doesn't have to be "inset". Inset has two particularly good use cases. Clipping blocks of an element and using it as a "controlled" overflow. Whereas overflow: hidden will hide everything outside the bounding box. We can use an inset clip-path to allow overflow in certain directions. And that's because we can use negative values with clip-path.

For example, this clip-path would allow overflow out of the top edge and not the others.

.overflow--top {
  clip-path: inset(-100% 0 0 0);
}
Enter fullscreen mode Exit fullscreen mode

Consider this demo of an animated rocket. We want the rocket to only be clipped from the bottom as it comes out of the opening. This is a good use case for controlled overflow.

The last thing to mention for inset is that you can apply a corner radius. To do this, use round followed by a radius. This works with short-hand much like padding, margin, etc.

For example,

.rounded-inset {
  clip-path: inset(0 0 50% 0 round 10% 25% 50% 0%);
}
.rounded-inset {
  clip-path: inset(0 0 50% 0 round 10% 25%);
}
Enter fullscreen mode Exit fullscreen mode

Have a play with this demo to see how controlled overflow can work. Rounded corners are applied in the demo and notice how they disappear at certain values.

Circle

Circle clips aren't ones that come up often. This is partly due to the fact we can achieve the same result with the use of border-radius in many cases.

.circle-clip {
  clip-path: circle(50%);
}
Enter fullscreen mode Exit fullscreen mode

The value for circle is the radius relative to the element. A 50% radius will create a circle that covers an element. Equal to using this.

.circle-clip {
  border-radius: 50%;
  overflow: hidden;
}
Enter fullscreen mode Exit fullscreen mode

The magic with using circle is when we define both a radius and a position.

.clipped-offset-circle {
  clip-path: circle(50% at 100% 25%);
}
Enter fullscreen mode Exit fullscreen mode

Those two final values are position x and position y. The use of positioning is what gives us interesting use cases for circle clipping. This defaults to 50% 50% if not defined.

For example, how about an image reveal on :hover? In this demo, we overlay two images. Then we reveal a color version using a transitioned clip-path. Play with the values to make the image bloom from different positions.

Here's the same demo without the reveal. It will get you comfortable with circle clips. Try changing the positions and radius.

Ellipse

The ellipse value works almost exactly the same as circle. The only difference is that we get to define both a horizontal and vertical radius. Again, the position is optional.

.ellipse-clip {
  clip-path: ellipse(50% 25% at 50% 50%);
}
Enter fullscreen mode Exit fullscreen mode

Try it out!

Polygon

Now things get interesting. The polygon clip allows you to define a polygon with as many points as you like for clipping an element. Each point is a coordinate relative to the element. When approaching a polygon clip, try walking the coordinates in your head. This I find is the best approach for polygon paths.

For example, start with this basic polygon.

.polygon-clip {
  clip-path: polygon(0 0, 100% 0, 100% 100%, 0 100%);
}
Enter fullscreen mode Exit fullscreen mode

That's right! It would be the same as inset(0 0 0 0). The clip we defined right at the top of this article?

.clipped {
  clip-path: polygon(100% 0, 20% 50%, 35% 50%, 0% 100%, 70% 50%, 50% 50%);
}
Enter fullscreen mode Exit fullscreen mode

This would give you a thunderbolt like shape!

The cool thing about polygon is that you can create any polygon you can think of. For fun, I recreated the ever-popular "Shapes of CSS" article shapes with polygon clips.

Try adding and removing nodes in this demo to make different polygons.

You may have noticed something when playing with the nodes. You can create "faux" breaks in the path depending on the route you take.

If you cross the paths between nodes, you're able to cut parts away.

If you duplicate some of the points and walk a line, you can create separated shapes.

This has the benefit of maintaining responsiveness.

Path

For everything else with clip-path, there's path. This one's the most flexible. It's now supported in all the major browsers! But, it has its caveats. Using a path value means passing in a path definition string. This is the same path we use for an SVG path. And it's relative to the dimensions of our element.

/* Any guess at what shape this is? */
.path-clipped {
  clip-path: path("M 10,30
           A 20,20 0,0,1 50,30
           A 20,20 0,0,1 90,30
           Q 90,60 50,90
           Q 10,60 10,30 z")
}
Enter fullscreen mode Exit fullscreen mode

It means we can create some interesting effects that could otherwise be very tricky. The alternative would be reaching for SVG or using CSS masking.

Consider this clip. It's a sunshine clip. The path breaks into different segments. This is something we can't achieve with the other clip values. Unless we use a lot of Math or the "faux" technique we mentioned with polygon. We're combining rounded shapes with polygons too. This is the power of using path. The ability to create irregular shapes or paths that break. This gives us lots of opportunity. To note, I created the path there by resizing an SVG icon in Figma, and then lifting the path definition out of the file. That took maybe a minute or so.

The caveat to using path is the path definition itself. As mentioned, it's relative to the dimensions of our element.
This is where things get tricky. It's not responsive. A path definition uses pixels that are relative to an SVG viewBox. When applied to an element, the element's width and height become an implied viewBox. This is the same hurdle that CSS motion path faces. I wrote about ways to tackle this before. The best approach if we decide to use path is to go with concrete sizing. Or create scaled versions of our path to complement.

We should only reach for path when we need very irregular shapes. The lack of responsiveness adds a hurdle. With that in mind, if we can create the shape we need with regular "responsive" clips and shapes, do that. Alternatively, use SVG or CSS masking if possible.


Animation && Transition

As seen in some of the demos above, we can transition or animate clip-path. There's one condition. The path must have a consistent structure. For example, if we transition a polygon, that polygon must have a consistent number of points.

Consider this "Avengers" themed animation that cycles through different polygon clips.

This demo for image reveals showcases a variety of different shapes being transitioned. The "start" and "end" clips are inlined as CSS variables for each image container.

This will even work with path paths. Try hovering over the moon here.

The key thing is that the paths transitioned to and from have the same number of nodes or points. And that they have the same type of clip-path.

Case Studies && Use Cases

There isn't a great place to put these observations. But, "Case Studies" kinda feels right. These are things that could be worth noting and make you consider approaches. In particular, whether clip-path is right for the job.

Reveal Scenarios

The use of clip-path is perfect for any type of "Reveal" scenario. This is where we can make a clear distinction between a reveal and a scale. A reveal does not distort its content.

Consider this demo. It's a Twitch stream overlay concept where the banners animate in.

But, the transition uses scaleX and that distorts the banner content. This is a great use case for a reveal.

In that demo, we're doing this.

@keyframes growIn {
  from {
    transform: rotate(calc(var(--rotate, 0) * 1deg)) scaleX(0);
  }
}
Enter fullscreen mode Exit fullscreen mode

But, it would make more sense if we switched that animation around. For this, we could use scoped variables.

.banner {
  clip-path: inset(0 0 0 0);
}
.banner--horizontal {
  --clip: inset(0 0 0 100%);
}
.banner--vertical {
  --clip: inset(0 100% 0 0);
}
@keyframes growIn {
  from {
    clip-path: var(--clip);
  }
}
Enter fullscreen mode Exit fullscreen mode

And now our banners would reveal the information and not distort it!

Reveals make a great use case for clip-path usage. We can use this image reveal demo again for another example.

Skewed Sections

This design phenomenon has taken off in recent years. The skewing of page sections and content. I got thinking about this when approached about how to create a certain effect. Let's look at some examples.

Consider this page with some basic sections.

We want each division to have an angle. It's tempting to reach for a clip-path here. Using polygon would seem apt.

section {
  clip-path: polygon(0 20%, 100% 0%, 100% 80%, 0 100%);
}
Enter fullscreen mode Exit fullscreen mode

And, that works to an extent. All we'd need is a way to cover those corners for the first section.

We could change it so that it's applied to even sections. But, then we'll get an issue at the end of the document.

What if want to apply a background color to every section? That's tricky because the sections don't meet now that they're clipped.

We could make use of pseudo-elements and use coordinates that go outside the bounds of the section. But, that could get complicated and hard to maintain. We have to start managing overlaps and using extra elements. Plus we need to calculate the angle.

The trick here is to think about what we're trying to do. The clue is in the goal. We want to skew the sections. And CSS transforms will let us do this.

section {
  transform: skewY(-11deg);
}
section > * {
  transform: skewY(11deg);
}
Enter fullscreen mode Exit fullscreen mode

That small snippet of CSS gets us most of the way and we don't need to handle clip management. This is a rudimentary approach.

Take it a little further with pseudo-elements and you've got something quite usable.

In fact, Nils Binder covers different ways to approach these diagonal sections. This playground using the transform approach is perfect and handles how to cover the corners, etc.

The gist here is that because we can with clip-path doesn't mean we should. It's an interesting case of looking at different ways to approach the same problem. Something that often comes up when we do things with CSS.

Glitchy Effects

Glitchy effects are a great use case for using clip-path. Because we can animate a clip-path, moving an inset clip over an element can create the effect. It's what's used for these CSS Cyberpunk 2077 buttons.

The "trick" for animated glitch effects is using an animated clip on a clone element.

A few steps later with the buttons and we get to this.

You can read about how to make them here.

That's It!

That's all you might need to know about clip-path... for now. Got a cool demo or a use case that's of interest. Share it with me!

Discussion (0)

pic
Editor guide