Skip to main content

CSS Specificity and Cascade

Understanding CSS Specificity and Cascade​

CSS Specificity and Cascade are fundamental concepts in CSS that dictate how our styles are applied to our HTML elements. This tutorial will break down these concepts in a step-by-step manner, making it easy for beginners to grasp.

What is CSS Specificity?​

Specificity is the means by which browsers decide which CSS property values are the most relevant to an element and, therefore, will be applied.

Every selector in CSS has a specificity value. If multiple selectors are targeting the same HTML element, the one with the highest specificity will take precedence, regardless of the order they appear in the CSS file.

Here's how specificity values are calculated:

  • Type selectors (e.g., h1) and pseudo-elements (e.g., ::before) have a specificity of 0,0,0,1.
  • Class selectors (e.g., .example), attributes selectors (e.g., [type="radio"]) and pseudo-classes (e.g., :hover) have a specificity of 0,0,1,0.
  • ID selectors (e.g., #example) have a specificity of 0,1,0,0.
  • Inline styles added to an element (e.g., style="font-weight:bold") directly have a specificity of 1,0,0,0.

The universal selector (*), combinators (+, >, ~, ' ') and negation pseudo-class (:not()) have no effect on specificity.

What is CSS Cascade?​

The cascade is the process of combining different stylesheets and resolving conflicts between different CSS rules and declarations, when more than one rule applies to a certain element.

Here's how the browser decides which rule to apply:

  • Importance: Styles marked with !important take precedence over other styles.
  • Specificity: If importance is the same, the style with more specific selector wins.
  • Source Order: If both importance and specificity are the same, the style declared later in the CSS file wins.

Tips for Managing Specificity and Cascade​

  1. Avoid using !important: This is a powerful tool but can lead to hard-to-debug issues, as it overrides any other declarations. It's best to use it sparingly and only when absolutely necessary.

  2. Leverage Specificity, Don't Fight It: Instead of relying on !important or increasing the number of selectors, it's better to understand how specificity works and use it to your advantage.

  3. Keep It Simple: The simpler your CSS selectors, the easier it is to maintain and less likely to cause conflicts. This also makes your CSS more readable.

Conclusion​

Understanding CSS Specificity and Cascade is crucial to mastering CSS. It enables you to write more effective, efficient, and maintainable code. Keep practicing these concepts, and soon you'll be leveraging them like a pro!