CSS transition not working with underline
A proper solution that will work with multiple line text and doesn't require border-bottom mockup should look like this. It utilizes text-decoration-color property.
Have in mind that it's not supported by old browsers
.underlined-text{
text-decoration: underline;
text-decoration-color: transparent;
transition: 1s;
/*add those for opera and mozilla support*/
-webkit-text-decoration-color: transparent;
-moz-text-decoration-color: transparent;
}
.underlined-text:hover{
text-decoration-color: red;
/*add those for opera and mozilla support*/
-webkit-text-decoration-color: red;
-moz-text-decoration-color: red;
}<span class="underlined-text">You're the greatest thing that has ever been or ever will be. You're special. You're so very special. It is a lot of fun. You don't want to kill all your dark areas they are very important. In your world you can create anything you desire.</span>Updated for 2021:
The support for text-decoration-color has come a long way, and common browser support requirements have loosened making it a viable option for most new projects. If you are only seeking a color transition, and can do without IE support, see this answer below.
Original answer:
You cannot change the color of the text-decoration independent of the color. However, you can achieve a similar effect with pseudo elements:
.un {
display: inline-block;
}
.un::after {
content: '';
width: 0px;
height: 1px;
display: block;
background: black;
transition: 300ms;
}
.un:hover::after {
width: 100%;
}<span class="un">Underlined Text - Or to be underlined</span>That is the most customizable way to do it, you can get all sorts of transitions. (Try playing around with the margins/alignment. You can make some awesome effects without adding to your HTML)
But if you just want a simple underline, use a border:
.un {
transition: 300ms;
border-bottom: 1px solid transparent;
}
.un:hover {
border-color: black;
}<span class="un"> Underlined Text - Or to be underlined </span>