Animating the underlining of multi-line text

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Cassie Evans shows us how to combine background–size, a linear-gradient based background-image and a keyframe animation (all in HTML and CSS) for a lovely progressive underline effect on multi-line text.

Here’s the gist of it:

<h2>This is a multi-line spanning animated underline. This took an annoyingly long time to figure out.</h2>
body {
padding: 40vh 30vw;
font-family: cursive;
text-align: left;
font-size: 130%;

h2 {
line-height: 1.5;
display: inline;
background-image: linear-gradient(
transparent 50%,
#e1fffe 50%,
#b0f8ff 85%,
transparent 85%,
transparent 100%
background-repeat: no-repeat;
background-size: 0% 100%;
animation: animatedBackground 2s cubic-bezier(0.645, 0.045, 0.355, 1) 0.5s forwards;

@keyframes animatedBackground {
to {
background-size: 100% 100%;

Thanks, Cassie!

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