Day 22: the ::backdrop pseudo-element

It’s time to get me up to speed with modern CSS. There’s so much new in CSS that I know too little about. To change that I’ve started #100DaysOfMoreOrLessModernCSS. Why more or less modern CSS? Because some topics will be about cutting-edge features, while other stuff has been around for quite a while already, but I just have little to no experience with it.

You can use the ::backdrop pseudo-element to style the backdrop of modal dialogs and elements which have been placed in fullscreen mode using the Fullscreen API.

::backdrop {
  background-color: rgb(0 0 0 / 0.5);
}

show modal

You don't have to limit yourself to semi-transparent background color.

::backdrop {
  background: conic-gradient(red, orange, yellow, green, red);
  outline: 20px solid white;
  outline-offset: -20px;
}

show modal

See on CodePen.

Further reading

• ::backdrop on MDN