Question

Is it possible to create a circle using only HTML5 / CSS3 which has a border that only goes part way around the circle? If not, what techniques can I use to accomplish this effect? I would prefer to use pure DOM elements, but if I have to I can draw on canvas or spin up an SVG.

Answer 1

2023 solution

This method requires no JS, no extra element and not even any pseudos, just a handful of CSS declarations. It also works if the element has a (semi)transparent background in addition to this partial border.

It uses a two layer mask, one being a conic-gradient which creates a visible pie selection and whose size is relative to the border-box and the second being a simple full cover layer restricted to the padding-box.

First, we make our element circular (arbitrary width, an aspect-ratio of 1 and a border-radius set to 50%) and give it a border.

Then, we set a mask that’s a conic-gradient(), relative to the border-box, covering a percentage --p of our element (by default starting from 12 o’clock and going clockwise).

On top of this mask layer, we set a full cover one restricted to the padding-box.

.circular-progress {
  border: solid 1.5em hotpink;
  width: 50vmin;
  aspect-ratio: 1;
  border-radius: 50%;
  background: hsla(180, 100%, 50%, .5);
  --mask: 
    linear-gradient(red, red) padding-box, 
    conic-gradient(red var(--p, 17%), transparent 0%) border-box;
  -webkit-mask: var(--mask);
          mask: var(--mask)
}

/* just to make it obvious it works with semitrasparent background */
body {
  background: 
    url(https://images.unsplash.com/photo-1693483923875-cdd9ef4a8046?w=800) 
      50%/ cover
}

<div class='circular-progress'></div>

If we want to animate this, we need to also register --p.

@property --p {
  syntax: '<percentage>';
  initial-value: 0%;
  inherits: true
}

.circular-progress {
  border: solid 1.5em hotpink;
  width: 50vmin;
  aspect-ratio: 1;
  border-radius: 50%;
  background: hsla(180, 100%, 50%, .5);
  --mask: 
    linear-gradient(red, red) padding-box, 
    conic-gradient(red var(--p), transparent 0%) border-box;
  -webkit-mask: var(--mask);
          mask: var(--mask);
  animation: p 4s linear infinite
}

@keyframes p { to { --p: 100% } }

/* just to make it obvious it works with semitrasparent background */
body {
  background: 
    url(https://images.unsplash.com/photo-1693483923875-cdd9ef4a8046?w=800) 
      50%/ cover
}

<div class='circular-progress'></div>

Registering custom properties this way in order to animate them is supported in Chromium browsers and in Safari and it’s coming soonish in Firefox Nightly too.

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Original answer from 2012 (preserved for web history reasons)

Yes, it is possible – see this:

.circle {
  position: relative;
  margin: 7em auto;
  width: 16em;
  height: 16em;
  border-radius: 50%;
  background: lightblue;
}

.arc {
  overflow: hidden;
  position: absolute;
  /* make sure top & left values are - the width of the border */
  /* the bottom right corner is the centre of the parent circle */
  top: -1em;
  right: 50%;
  bottom: 50%;
  left: -1em;
  /* the transform origin is the bottom right corner */
  transform-origin: 100% 100%;
  /* rotate by any angle */
  /* the skew angle is 90deg - the angle you want for the arc */
  transform: rotate(45deg) skewX(30deg);
}

.arc:before {
  box-sizing: border-box;
  display: block;
  border: solid 1em navy;
  width: 200%;
  height: 200%;
  border-radius: 50%;
  transform: skewX(-30deg);
  content: '';
}

<div class='circle'>
  <div class='arc'></div>
</div>