CSS specificity determines which styles win when multiple rules target the same element. Master this and you'll never use !important again.
The Specificity Hierarchy
Calculating Specificity
The :where() and :is() Difference
Cascade Layers
Common Mistakes
- !important wars: If you need !important, your architecture is wrong. Use cascade layers instead.
- Over-qualifying selectors:
div.container > ul > li > a.linkis fragile. Use.nav-link. - Relying on source order: Source order only matters when specificity is equal.
Modern Best Practices
- Use cascade layers for architectural specificity control
- Use
:where()for low-specificity defaults - Prefer classes over IDs for styling
- Use BEM or utility classes to keep specificity flat