Optimizing Web Fonts for Faster Page Loads and Better Ad Performance

Web font optimization is an essential aspect of improving website performance. With users demanding faster load times and a smoother browsing experience, optimizing fonts can significantly reduce page load times and improve the performance of ads. Faster pages lead to better user experiences and improved ad delivery. This article will guide you through various strategies to optimize web fonts, reducing costs and increasing revenue through more efficient ad performance.

1. Font Hosting: Self-Hosted vs. Third-Party Fonts

The first step in optimizing web fonts is deciding whether to host them yourself or use a third-party provider like Google Fonts. Each option has its benefits and challenges:

Third-Party Fonts: While services like Google Fonts are convenient, they come with some drawbacks. For instance, cross-site caching—once a major advantage—is no longer available due to privacy concerns. With third-party hosting, you have limited control over font delivery, and it can introduce additional network requests.
Self-Hosting Fonts: Hosting fonts on your own server gives you full control over the files, allowing you to optimize and serve only what’s needed. This can result in faster load times, particularly when paired with additional performance techniques like font subsetting and caching.

2. Reducing the Number of Fonts

The more fonts you load, the more data the browser needs to fetch, and the longer it takes to display content. Reducing the number of fonts you use can have a significant impact on performance.

Use System Fonts: If possible, consider switching to system fonts. These are fonts already installed on users’ devices, so there’s no need to load external font files. For example, SF Pro for Mac, Segoe UI for Windows, and Ubuntu for Linux are widely supported system fonts that can be used to ensure consistency across browsers without adding additional weight.
Custom Fonts: If custom fonts are important for branding, limit the number of fonts you load and avoid unnecessary weights and styles.

3. Reducing Font File Sizes

Large font files can slow down your website significantly. Reducing the size of these files is crucial for performance.

Use WOFF2 Format: The WOFF2 format is more compressed than TTF or OTF, which helps reduce file sizes. It’s the preferred format for modern web browsers.
Font Subsetting: You only need to load the characters that your website actually uses. By using tools like glyphhanger, you can create custom font subsets that exclude unused characters, reducing the size of font files.

Example: Removing Unused Characters

Consider a scenario where you only need Latin characters for your website. By creating a subset that includes just those characters, you can reduce the font file size by removing characters you don’t need.

glyphhanger --subset=font.woff2 --format=woff2 --LATIN

This ensures that only the necessary character set is included, reducing the file size.

4. Optimizing Weights and Widths in Variable Fonts

One of the most powerful strategies for reducing font file sizes is using variable fonts. These fonts allow multiple styles (e.g., regular, bold, italic) to be combined into a single file. While this reduces the number of font files needed, there’s still a significant amount of optimization you can do by eliminating unused font axes, such as weights and widths.

Understanding Weights and Widths in Variable Fonts

Weights Axis: The weights axis controls the thickness of the font, ranging from thin to bold. However, websites rarely use all available weights. For instance, if you only need the regular and bold weights, you can eliminate all the intermediate weights, which will significantly reduce the font file size.
Widths Axis: Similar to weights, the widths axis controls the horizontal stretching of the font. If your website only uses one width (e.g., normal), eliminating other width variants can further reduce the file size.

Optimizing Weights and Widths

You can use font editing tools like the Axis Editor or Slice (from Source Foundry) to eliminate unnecessary weights and widths.

Axis Editor: This tool allows you to select which weights and widths are used in your variable font. You can eliminate unused values to reduce the font file size.
CSS Font-Weight Range: Use the CSS font-weight property to specify exactly which weights are used on your website. You can then tailor the font file to include only those weights.

Example: Reducing Weights and Widths for Source Sans Pro

Let’s say you’re using Source Sans Pro as a variable font, and you only need the regular and bold weights, with a normal width. Instead of using the entire variable font file, you can remove the intermediate weights and widths.

Original File Size (WOFF2): 214 KB
⁠After Reducing Weights and Widths: 166 KB

This 22% reduction in file size can make a significant difference in performance.

5. Font Display and Loading Strategies

How fonts are displayed and loaded can impact both performance and user experience. Here are the main strategies:

Font-Display Property

The font-display property controls how a font is rendered while it’s loading. The most common values are:

swap: This ensures that text is displayed using a fallback font until the web font is loaded. While this improves rendering speed, it can cause layout shifts.
optional: This is the best option for performance. If the web font isn’t loaded within 100 milliseconds, the browser will use the fallback font and won’t swap back to the web font once it’s loaded.
block: This value blocks rendering of text until the font is fully loaded, which can cause delays.

Preloading Fonts

Use the <link rel="preload"> tag to prioritize font loading. This allows the browser to fetch the font earlier in the loading process, improving render times.

<link
  rel="preload"
  href="/fonts/myfont.woff2"
  as="font"
  type="font/woff2"
  crossorigin="anonymous">

6. Managing Layout Shifts (CLS)

Cumulative Layout Shift (CLS) is a metric that tracks unexpected layout shifts during page load. To minimize CLS caused by fonts:

Font-Size Adjustment: Use CSS properties like font-size-adjust and size-adjustment to ensure that fonts are rendered similarly to how the page was designed, even if they haven’t fully loaded.
Line Height and Letter Spacing: Properly adjusting these properties helps prevent layout shifts.

Conclusion

Optimizing web fonts is a critical step in improving both user experience and ad performance. By choosing the right hosting strategy, reducing font file sizes, and carefully managing font weights and widths, you can dramatically improve page load times. These optimizations not only make your site faster, but they also improve ad performance, leading to better revenue and lower costs.

Whether you’re developing a website or managing ads, implementing these font optimization techniques will help you stay ahead in the competitive digital space.

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