How do you optimize web fonts for performance?

Optimizing web fonts is crucial for enhancing the performance of a website, especially when aiming for the best user experience and fast load times. When web fonts are not optimized, they can lead to increased page load times and affect the rendering of the webpage content. Here's how you can optimize web fonts for better performance:

1. Choose the Right Font Formats: Use modern font formats like WOFF2 which are highly compressed and supported by most browsers.
2. Subset Fonts: Only include the characters you need. For example, if your site predominantly uses English, you might not need the entire set of characters from other languages.
3. Use Font Loading Strategies: Implement font-display to control how fonts are displayed during loading. Options like swap can be used to ensure text remains visible during font loading.
4. Preload Fonts: Use the <link rel="preload"> tag to load fonts earlier in the page load process.
5. Host Fonts Locally: This can reduce latency and increase reliability compared to using third-party services like Google Fonts.

Key Talking Points:

• Use Modern Formats: Prefer WOFF2 over older formats like TTF or OTF.
• Subset Fonts: Include only the required glyphs.
• Font Display Strategy: Use font-display: swap to prevent invisible text.
• Preload Fonts: Speed up font loading by preloading.
• Self-host Fonts: Reduce dependencies on external services.

NOTES:

Reference Table: Font Formats

Follow-Up Questions and Answers:

1. What is the impact of font loading on perceived performance?

   • Answer: Fonts can significantly impact perceived performance due to the "Flash of Invisible Text" (FOIT) or "Flash of Unstyled Text" (FOUT). Using font-display: swap helps mitigate FOIT by allowing text to be visible with fallback fonts until the custom font loads.

2. Can you explain the font-display property and its values?

   • Answer: font-display is a CSS property that defines how a font is displayed. Its values include:
     • auto: Default behavior of the browser.
     • block: Invisible text until the font is loaded.
     • swap: Uses fallback until the font is ready.
     • fallback: Short block period, then swap to fallback.
     • optional: Gives the browser flexibility to choose.