CSS if() Explained: Conditional Logic with No JavaScript

CSS now supports conditional logic through the if() function, enabling developers to make decisions directly in stylesheets without JavaScript. The function works with three query types: style queries (testing CSS variables or computed styles), media queries (responsive viewport conditions), and supports queries (browser feature detection). Each condition can return different values, with optional fallback values using else. While powerful for surgically changing property values based on applied styles, viewport size, or browser capabilities, browser support remains limited as of 2025 and may not be production-ready for all projects.