Single Element Loaders: The Spinner

Making CSS-only loaders is one of my favorite tasks. It’s always satisfying to look at those infinite animations. And, of course, there are lots of techniques and approaches to make them — no need to look further than CodePen to see just how many. In this article, though, we will see how to make a single element loader writing as little code as possible.

I have made a collection of more than 500 single div loaders and in this four-part series, I am going to share the tricks I used to create many of them. We will cover a huge number of examples, showing how small adjustments can lead to fun variations, and how little code we need to write to make it all happen!

For this first article, we are going to create a one of the more common loader patterns: spinning bars:

Here’s the approach

A trivial implementation for this loader is to create one element for each bar wrapped inside a parent element (for nine total elements), then play with opacity and transform to get the spinning effect.

My implementation, though, requires only one element:

<div class="loader"></div>

…and 10 CSS declarations:

.loader {
  width: 150px; /* control the size */
  aspect-ratio: 1;
  display: grid;
  mask: conic-gradient(from 22deg, #0003, #000);
  animation: load 1s steps(8) infinite;
}
.loader,
.loader:before {
  --_g: linear-gradient(#17177c 0 0) 50%; /* update the color here */
  background: 
    var(--_g)/34% 8%  space no-repeat,
    var(--_g)/8%  34% no-repeat space;
}
.loader:before {
  content: "";
  transform: rotate(45deg);
}
@keyframes load {
  to { transform: rotate(1turn); }
}

Let’s break that down

At first glance, the code may look strange but you will see that it’s more simple than what you might think. The first step is to define the dimension of the element. In our case, it’s a 150px square. We can put aspect-ratio to use so the element stays square no matter what.

.loader {
  width: 150px; /* control the size */
  aspect-ratio: 1; /* make height equal to width */
}

When building CSS loaders, I always try to have one value for controlling the overall size. In this case, it’s the width and all the calculations we cover will refer to that value. This allows me to change a single value to control the loader. It’s always important to be able to easily adjust the size of our loaders without the need to adjust a lot of additional values.

Next, we will use gradients to create the bars. This is the trickiest part! Let’s use one gradient to create two bars like the below:

background: linear-gradient(#17177c 0 0) 50%/34% 8% space no-repeat;

Our gradient is defined with one color and two color stops. The result is a solid color with no fading or transitions. The size is equal to 34% wide and 8% tall. It’s also placed in the center (50%). The trick is the use of the keyword value space — this duplicates the gradient, giving us two total bars.

From the specification:

The image is repeated as often as will fit within the background positioning area without being clipped and then the images are spaced out to fill the area. The first and last images touch the edges of the area.

I am using a width equal to 34% which means we cannot have more than two bars (3*34% is greater than 100%) but with two bars we will have empty spaces (100% - 2 * 34% = 32%). That space is placed in the center between the two bars. In other words, we use a width for the gradient that is between 33% and 50% to make sure we have at least two bars with a little bit of space between them. The value space is what correctly places them for us.

We do the same and make a second similar gradient to get two more bars at the top and bottom, which give us a background property value of:

background: 
 linear-gradient(#17177c 0 0) 50%/34% 8%  space no-repeat,
 linear-gradient(#17177c 0 0) 50%/8%  34% no-repeat space;

We can optimize that using a CSS variable to avoid repetition:

--_g: linear-gradient(#17177c 0 0) 50%; /* update the color here */
background: 
 var(--_g)/34% 8%  space no-repeat,
 var(--_g)/8%  34% no-repeat space;

So, now we have four bars and, thanks to CSS variables, we can write the color value once which makes it easy to update later (like we did with the size of the loader).

To create the remaining bars, let’s tap into the .loader element and its ::before pseudo-element to get four more bars for a grand total of eight in all.

.loader {
  width: 150px; /* control the size */
  aspect-ratio: 1;
  display: grid;
}
.loader,
.loader::before {
  --_g: linear-gradient(#17177c 0 0) 50%; /* update the color here */
  background: 
    var(--_g)/34% 8%  space no-repeat,
    var(--_g)/8%  34% no-repeat space;
}
.loader::before {
  content: "";
  transform: rotate(45deg);
}

Note the use of display: grid. This allows us to rely on the grid’s default stretch alignment to make the pseudo-element cover the whole area of its parent; thus there’s no need to specify a dimension on it — another trick that reduces the code and avoid us to deal with a lot of values!

Now let’s rotate the pseudo-element by 45deg to position the remaining bars. Hover the following demo to see the trick:

Setting opacity

What we’re trying to do is create the impression that there is one bar that leaves a trail of fading bars behind it as it travels a circular path. What we need now is to play with the transparency of our bars to make that trail, which we are going to do with CSS mask combined with a conic-gradient as follows:

mask: conic-gradient(from 22deg,#0003,#000);

To better see the trick, let’s apply this to a full-colored box:

The transparency of the red color is gradually increasing clockwise. We apply this to our loader and we have the bars with different opacity:

In reality, each bar appears to fade because it’s masked by a gradient and falls between two semi-transparent colors. It’s hardly noticeable when this runs, so it’s sort of like being able to say that all the bars have the same color with a different level of opacity.

The rotation

Let’s apply a rotation animation to get our loader. Note, that we need a stepped animation and not a continuous one that’s why I am using steps(8). 8 is nothing but the number of the bars, so that value can be changed depending on how many bars are in use.

.loader {
  animation: load 3s steps(8) infinite;
}

/* Same as before: */
@keyframes load {
  to { transform: rotate(1turn) }
}

That’s it! We have our loader with only one element and a few lines of CSS. We can easily control its size and color by adjusting one value.

Since we only used the ::before pseudo-element, we can add four more bars by using ::after to end with 12 bars in total and almost the same code:

We update the rotation of our pseudo-elements to consider 30deg and 60deg instead of 45deg while using an twelve-step animation, rather than eight. I also decreased the height to 5% instead of 8% to make the bars a little thinner.

Notice, too, that we have grid-area: 1/1 on the pseudo-elements. This allows us to place them in the same area as one another, stacked on top of each other.

Guess what? We can reach for the same loader using another implementation:

Can you figure out the logic behind the code? Here is a hint: the opacity is no longer handled with a CSS mask but inside the gradient and is also using the opacity property.

Why not dots instead?

We can totally do that:

If you check the code, you will see that we’re now working with a radial gradient instead of a linear one. Otherwise, the concept is exactly the same where the mask creates the impression of opacity, but we made the shapes as circles instead of lines.

Below is a figure to illustrate the new gradient configuration:

If you’re using Safari, note that the demo may be buggy. That’s because Safari currently lacks support for the at syntax in radial gradients. But we can reconfigure the gradient a bit to overcome that:

.loader,
.loader:before,
.loader:after {
  background:
    radial-gradient(
      circle closest-side,
      currentColor 90%,
      #0000 98%
    ) 
    50% -150%/20% 80% repeat-y,
    radial-gradient(
      circle closest-side,
      currentColor 90%,
      #0000 98%
    ) 
    -150% 50%/80% 20% repeat-x;
}

More loader examples

Here is another idea for a spinner loader similar to the previous one.

For this one, I am only relying on background and mask to create the shape (no pseudo-elements needed). I am also defining the configuration with CSS variables to be able to create a lot of variations from the same code — another example of just the powers of CSS variables. I wrote another article about this technique if you want to more details.

Note that some browsers still rely on a -webkit- prefix for mask-composite with its own set of values, and will not display the spinner in the demo. Here is a way to do it without mast-composite for more browser support.

I have another one for you:

For this one, I am using a background-color to control the color, and use mask and mask-composite to create the final shape:

Before we end, here are some more spinning loaders I made a while back. I am relying on different techniques but still using gradients, masks, pseudo-element, etc. It could be a good exercise to figure out the logic of each one and learn new tricks at the same time. This said, if you have any question about them, the comment section is down below.

Wrapping up

See, there’s so much we can do in CSS with nothing but a single div, a couple of gradients, pseudo-elements, variables. It seems like we created a whole bunch of different spinning loaders, but they’re all basically the same thing with slight modifications.

This is only the the beginning. In this series, we will be looking at more ideas and advanced concepts for creating CSS loaders.