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What are CSS custom properties and how do they differ from variables in preprocessors like Sass?
Asked on Apr 27, 2026
Answer
CSS custom properties, often referred to as CSS variables, allow you to store values that can be reused throughout your stylesheet. Unlike variables in preprocessors like Sass, CSS custom properties are dynamic and can be manipulated with JavaScript in real-time.
Example Concept: CSS custom properties are defined using the "--" prefix and are accessed using the "var()" function. They are part of the DOM, which means they can be updated and read by JavaScript, offering real-time flexibility. In contrast, Sass variables are static and are compiled at build time, meaning they cannot be changed after the CSS is generated.
Additional Comment:
- CSS custom properties are defined within a selector, typically at the root level using ":root" for global scope.
- They cascade and inherit like other CSS properties, allowing for more dynamic styles.
- Sass variables are more powerful for complex logic and functions during the preprocessing stage but lack runtime flexibility.
- Use CSS custom properties for dynamic theming and runtime changes, while Sass variables are best for build-time logic and structure.
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