#atom

Subtitle:

Strategies to deliver web fonts efficiently while maintaining visual stability

Core Idea:

Font optimization involves implementing techniques that balance aesthetic typography choices with performance considerations, focusing on preventing layout shifts and ensuring rapid text rendering.

Key Principles:

1. Visual Stability Preservation:
   • Ensuring text doesn't shift layout when custom fonts load, preventing poor user experience.
2. Progressive Enhancement:
   • Starting with system fonts while loading custom fonts in the background, optimizing for both speed and aesthetics.
3. Resource Prioritization:
   • Strategically loading only necessary font files, weights, and character subsets based on actual usage.

Why It Matters:

• Layout Shift Prevention:
  • Unoptimized fonts are a leading cause of Cumulative Layout Shift (CLS), frustrating users when text jumps during reading.
• Perceived Performance:
  • Fast-rendering text dramatically improves perceived loading speed even when other elements are still loading.
• Bandwidth Efficiency:
  • Well-optimized font strategies can reduce font payload by 60-90%, particularly important for mobile users.

How to Implement:

1. Font Display Strategies:
   • Use font-display: swap to show text immediately with system fonts while custom fonts load in the background.
2. Font Matching Techniques:
   • Implement size-adjusted fallback fonts that match the dimensions of custom fonts to prevent layout shifts.
3. Preloading Critical Fonts:
   • Use resource hints to prioritize loading of essential font files before other resources.

Example:

• Scenario:

  • A text-heavy blog that uses custom fonts but experiences layout shifts during loading.

• Application:

  • Implementing font size adjustments and preloading:

  <!-- Preload the primary font file -->
  <link rel="preload" href="/fonts/custom-font.woff2" as="font" type="font/woff2" crossorigin>
  
  <style>
    /* Define the custom font */
    @font-face {
      font-family: 'CustomFont';
      src: url('/fonts/custom-font.woff2') format('woff2');
      font-display: swap;
    }
    
    /* Create a size-adjusted fallback font */
    @font-face {
      font-family: 'CustomFontFallback';
      src: local('Arial');
      size-adjust: 108%;
      ascent-override: 90%;
      descent-override: 22%;
      line-gap-override: 0%;
    }
    
    /* Use the font-family with fallback */
    body {
      font-family: 'CustomFont', 'CustomFontFallback', sans-serif;
    }
  </style>
  

• Result:

  • CLS reduced from 0.18 to 0.02, eliminating visible text jumps while maintaining the desired typography design.

Connections:

• Related Concepts:
  • Cumulative Layout Shift (CLS): Font optimization directly impacts layout stability metrics.
  • Resource Hints: Preload, prefetch, and other hints are essential tools for font optimization.
• Broader Concepts:
  • Web Performance Optimization: Font optimization is a critical component of overall site performance.
  • Typography on the Web: Balancing design intentions with performance considerations.

References:

1. Primary Source:
   • Google Web Fundamentals on Web Font Optimization
2. Additional Resources:
   • Stoon Stefanov's research on font metrics matching (mentioned in transcript)
   • Next.js font optimization documentation for automatic metric adjustments

Tags:

#web-performance #typography #fonts #optimization #layout-shift #web-vitals #frontend

Connections:

Sources:

• From: Syntax - Explicación de Web Vitals