How do I animate a CSS gradient stop with a smooth transition to transparent?

Question

I have the code bellow. How do I transition the gradient stop smoothly? Its just abruptly changing from one to another.

Most examples of gradient animations I have seem use the gradient position, but I believe changing the gradient stop should be possible too.

.test {
    display: inline-block;
    width: 300px;
    height: 300px;
    border-radius: 100%;
    background: conic-gradient(red, red);
    background-repeat: no-repeat;
    background-size: cover;
    background-position: center center;
    background-size: auto;
    -webkit-mask:radial-gradient(circle, transparent 50%, white calc(50% + 1px));

    animation:
        rotate
        4.5s
        ease-out
        0s
        infinite
        none
        running;
}

@keyframes rotate {
    0% {
        background-image: conic-gradient(red, red);
    }

    30% {
        background-image: conic-gradient(red 70%, transparent);
    }

    70% {
        background-image: conic-gradient(red 30%, transparent, transparent, transparent);
    }

    100% {
        background-image: conic-gradient(red, transparent);
    }
}

<div class="test"></div>

Does this answer your question? [Use CSS3 transitions with gradient backgrounds](https://stackoverflow.com/questions/6542212/use-css3-transitions-with-gradient-backgrounds) — Mahozad, May 15 '22 at 07:10

score 7 · Accepted Answer · answered Dec 03 '20 at 21:18

This as of Dec 03 2020 only works on Chrome or Edge 95+

One can animate the gradient using CSS @property.

@property --opacity {
  syntax: '<percentage>';
  initial-value: 100%;
  inherits: false;
}

.test {
    display: inline-block;
    position: absolute;
    border-radius: 100%;
    background-image: conic-gradient(
        red var(--opacity),
        red 10%,
        rgba(255, 0, 0, var(--opacity)),
        transparent,
        transparent
    );
    will-change: transform, background-image;
    width: 200px;
    height: 200px;
    mask:radial-gradient(circle, transparent 47%, white calc(47% + 1px));
    -webkit-mask:radial-gradient(circle, transparent 47%, white calc(47% + 1px));

    animation:
        conic-gradient
            4.5s
            ease-out
            0s
            infinite
            none
            running;
}

@keyframes conic-gradient {
    50% {
        --opacity: 0%;
    }

    85% {
        --opacity: 100%;
    }
}

<div class="test"></div>

Temani Afif · Answer 2 · 2020-12-02T22:26:20.570

In this particular case you can animate the background-color layer like below:

.test {
    display: inline-block;
    width: 300px;
    height: 300px;
    border-radius: 100%;
    background: 
      conic-gradient(red, transparent)
      red;
    -webkit-mask:radial-gradient(circle, transparent 50%, white calc(50% + 1px));

    animation:
        rotate
        4.5s
        ease-out
        0s
        infinite
        none
        running;
}
@keyframes rotate {
    100% {
        background-color:blue;
    }
}

<div class="test"></div>

UPDATE

Here is another idea combining opacity and gradient animation (a bit glitchy but will try to optimize it)

.test {
  display: inline-block;
  width: 300px;
  height: 300px;
  border-radius: 100%;
  background: conic-gradient(red 70%, transparent);
  animation: grad1 3s linear infinite;
  -webkit-mask: radial-gradient(circle, transparent 50%, white calc(50% + 1px));
  position: relative;
}

.test::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  opacity: 1;
  background: conic-gradient(red, red);
  animation: 
    op 1s   linear infinite,
    grad 3s linear infinite;
}

@keyframes op {
  100% {
    opacity: 0;
  }
}

@keyframes grad {
  0%,
  33.32% {
    background: conic-gradient(red, red);
  }
  33.328%,
  66.65% {
    background: conic-gradient(red 70%, transparent);
  }
  66.658%,
  100% {
    background: conic-gradient(red 30%, transparent);
  }
}

@keyframes grad1 {
  0%,
  33.32% {
    background: conic-gradient(red 70%, transparent);
  }
  33.328%,
  66.65% {
    background: conic-gradient(red 30%, transparent);
  }
  66.658%,
  100% {
    background: conic-gradient(red, transparent);
  }
}

<div class="test"></div>

This works, but not for my specific case because it's a transition to transparent, I edited the question, sorry about that. — user5507535, Dec 02 '20 at 16:28
Sure, replacing the color works, but how can I go from like `30%` to `70%`? I'm trying some options. — user5507535, Dec 02 '20 at 16:34
@user5507535 added another idea, not a perfect one but will try to make better — Temani Afif, Dec 02 '20 at 17:09

How do I animate a CSS gradient stop with a smooth transition to transparent?

2 Answers2

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