@cfpb/cfpb-design-system/src/elements/cfpb-utilities/skeleton.css

CFPB's UI framework

/*
This file defines a "loading skeleton", which is a wireframe-esque box that loads 
in before a web component has been initialized. 

Each component that has a loading skeleton also has a file similar to this one, 
which defines the dimensions of the box that should load. 

Having a loading skeleton avoids a layout shift when the component is actually 
initialized and rendered.
*/
*:not(:defined) {
  display: block;
  width: 100%;

  box-shadow: 0 0 3px rgb(90, 93, 97, 10%) inset;
  border-radius: 4px;

  animation: pulse-background 1.5s infinite;
}

@keyframes pulse-background {
  0% {
    background-color: transparent;
  }

  50% {
    background-color: rgb(90, 93, 97, 5%);
  }

  100% {
    background-color: transparent;
  }
}