CSS Outline

Last reviewed May 28, 2026 Content v20260528

This lesson

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

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

You will apply CSS Outline 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.

Outlines draw outside the border and are commonly used for focus indicators.

Never remove focus styles without a clear replacement. Keyboard users rely on visible focus.

Q: Border vs outline?
A: Outline does not take layout space; border does.
Q: Why do designers remove default outlines?
A: Visual preference, but it must be replaced with accessible custom focus styles.
Q: Good focus test?
A: Tab through controls and ensure focus is always visible at 200% zoom.

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

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