MDN’s freshly rebuilt front end delivers a cleaner interface, modern CSS, and a component‑driven architecture while honoring baseline web standards.

Modern UI Redesign

The new layout uses a grid‑based system and updated typography to improve readability across devices.

• Adopts CSS Grid for flexible page structures.
• Integrates web components for reusable UI blocks.
• Applies a high‑contrast color palette that meets WCAG AA criteria.
• Employs CSS custom properties for easy theming.
• Includes a lightweight dark‑mode toggle.

Baseline Feature Strategy

Only features marked "Widely available" are used directly; newer APIs are gated behind polyfills or progressive enhancement.

• Reference progressive enhancement guidelines.
• Detect support with CSS.supports() before applying advanced styles.
• Load polyfills on demand via dynamic import().
• Fallback to semantic HTML when a new API is unavailable.
• Log feature usage stats for future decisions.

Progressive Enhancement & Polyfills

Enhancements are layered on top of a solid base, ensuring every page remains functional on older browsers.

• Bundle polyfills with esbuild for minimal footprint.
• Use feature flags stored in localStorage to toggle experiments.
• Prioritize critical CSS to avoid layout shifts.
• Provide graceful degradation for JavaScript‑heavy widgets.
• Monitor fallback performance with Lighthouse audits.

Component‑Driven Architecture

Web components encapsulate markup, style, and behavior, making the codebase easier to maintain.

• Define custom elements with the class extends HTMLElement pattern.
• Scope styles using Shadow DOM to prevent leakage.
• Expose a clear API via attributes and events.
• Register components centrally in components.js.
• Document each component in the internal knowledge base.

Performance and Accessibility Tweaks

Every change is measured to keep load times low and navigation smooth for all users.

• Compress images with AVIF and serve via CDN.
• Leverage HTTP/2 multiplexing for parallel asset delivery.
• Implement prefetch for frequently visited docs.
• Audit ARIA roles with the axe‑core tool.
• Reference the project guide for future AI‑driven accessibility enhancements.