The CSSSupportsRule interface represents a single CSS @supports at-rule.

Inherits properties from its ancestors CSSConditionRule, CSSGroupingRule, and CSSRule.

Inherits methods from its ancestors CSSConditionRule, CSSGroupingRule, and CSSRule.

The CSS includes a CSS feature query using the @supports at-rule, containing one style rule. This will be the first CSSRule returned by document.styleSheets[0].cssRules. myRules[0] therefore returns a CSSSupportsRule object.

@supports (display: grid) {
  body {
    color: blue;
  }
}

let myRules = document.styleSheets[0].cssRules;
console.log(myRules[0]); // a CSSSupportsRule representing the feature query.

• @supports