CSS Specificity

Last reviewed May 28, 2026 Content v20260528

This lesson

This lesson teaches CSS Specificity—the ideas, syntax, and habits you need before moving on in CSS.

Without a solid grasp of CSS Specificity, you will repeat mistakes in CSS exercises and on real pages or scripts.

You will apply CSS Specificity in contexts like: All browser UIs, component libraries, marketing sites, and many native apps that reuse web views.

Read the lesson, edit HTML/CSS in the playground, press Run to preview, then answer the lesson MCQs.

When intermediate lessons feel comfortable and you are ready for production-style trade-offs.

Specificity determines which matching selector wins when multiple declarations target the same property.

.btn { color: #111827; }\n#checkout .btn { color: #dc2626; }\n.btn { color: #1d4ed8; }

The ID-based selector still wins. Later source order only wins when specificity ties.

Q: Why avoid IDs in component CSS?
A: Creates high-specificity locks that are hard to override cleanly.
Q: What breaks specificity ties?
A: Later source order.
Q: Practical strategy for manageable specificity?
A: Class-based selectors with shallow nesting and consistent component conventions.

Pitfall: Check cascade order—author stylesheet loses to inline styles and !important surprises.

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