aspect-ratio

The aspect-ratio property sets a preferred width-to-height ratio for an element's box.

Since CSS3 Spec ↗

Syntax

aspect-ratio: <width> / <height>;  /* e.g. 16 / 9 */

Examples

.video {
  width: 100%;
  aspect-ratio: 16 / 9;
}
.avatar { aspect-ratio: 1; width: 64px; }
Output
Renders a responsive 16:9 video frame and a perfectly square avatar.

Notes

Eliminates the old padding-top percentage hack and reserves space to prevent layout shift. If both width and height are set, aspect-ratio is ignored. Combine with object-fit for media.

Browser & runtime support

EnvironmentSince version
chrome 88
firefox 89
safari 15
edge 88

See also