Why Can't I Use CSS Variables in Media Queries?

Native CSS Variables Unavailable in Media Queries

Early users of CSS variables may encounter issues when attempting to incorporate them into media queries. A common approach like:

:root {
  --mobile-breakpoint: 642px;
}

@media (max-width: var(--mobile-breakpoint)) {

}

would not function as expected.

Behind the Scenes: CSS Specification Restrictions

According to the CSS specification, the var() function is only applicable within the values of properties. It is prohibited in other contexts, such as property names, selectors, or media queries. This explains why using it in media queries is invalid.

Operational Considerations

This limitation is logical. While CSS variables can be assigned to the root element (e.g., ) and inherited by descendants, media queries are not elements themselves and therefore lack the inheritance capability.

Alternative Solutions

CSS variables are not designed to address this specific use case. As a workaround, one can employ CSS preprocessors, which provide additional functionality and allow for variable usage in media queries.

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