The CSS data type describes the proportional relationship between a width and height. It is used As a value for the Aspect-ratio media feature in @media media queries, the Aspect-ratio size feature in @container container queries, and As a value for the CSS Aspect-ratio property....The <ratio> CSS data type describes the proportional relationship between a width and height. It is used as a value for the aspect-ratio media feature in @media media queries, the aspect-ratio size feature in @container container queries, and as a value for the CSS aspect-ratio property.