Published on April 24, 2025
Last Updated on July 1, 2025
Written by
Morgan Frank - Specialist in Page Speed
Fonts play a crucial role in your website’s design and branding, but they can also significantly impact page speed. Large font files, poorly chosen font loading strategies, and unnecessary font variations can all lead to slower rendering and a poorer user experience.
This guide covers key font optimization techniques: choosing web-safe fonts, subsetting, and implementing effective font loading strategies.
Before we delve into specifics, let’s highlight the crucial takeaways:
Key Takeaways
1. Web-Safe Fonts are a Fallback, Not a Primary Strategy:
2. Subsetting Reduces Font File Size:
3. font-display Controls Font Loading Behavior:
4. Preloading Critical Fonts:
5. Host Fonts Locally (If Possible):
Web-safe fonts are fonts that are pre-installed on a large percentage of operating systems. This means that if a user’s browser can’t download your custom web fonts (for whatever reason), the text will still be displayed using a web-safe font.
Common Web-Safe Fonts:
Using Web-Safe Fonts in CSS:
You should always specify web-safe fonts as fallbacks in your CSS font-family declarations. This is done by listing the fonts in order of preference, separated by commas.
body {
font-family: "MyCustomFont", Arial, sans-serif;
}
In this example:
Important: Web-safe fonts are fallbacks. They are not a primary font strategy. Relying solely on web-safe fonts severely limits your design options and can make your website look generic.
Font files, especially those for web fonts, can be surprisingly large. This is because they often contain hundreds or even thousands of characters (glyphs) – letters, numbers, symbols, and characters from different languages. In most cases, you’ll only use a small fraction of these characters on your website.
Subsetting is the process of creating a smaller version of a font file that only includes the characters you actually need.
Benefits of Subsetting:
Tools for Subsetting:
How to Subset:
1. Identify the characters you need: Analyze your website’s content and determine which characters are actually used. This might include:
2. Use a subsetting tool: Use one of the tools mentioned above to create a subset of your font file containing only the necessary characters.
3. Update your CSS: Update your CSS @font-face declarations to point to the subsetted font files.
How you load your fonts is just as important as choosing and subsetting them. Poor font loading strategies can lead to:
The font-display CSS property is your primary tool for controlling font loading behavior.
The font-display property tells the browser how to handle the display of text while a web font is loading. It accepts the following values:
@font-face {
font-family: "MyCustomFont";
src: url("my-font.woff2") format("woff2"),
url("my-font.woff") format("woff");
font-display: swap; /* Use the 'swap' value */
}Recommendation:
Preloading tells the browser to download specific font files early in the loading process, before they are actually needed by the CSS. This can significantly improve rendering speed, especially for critical fonts (those used for above-the-fold content).
You preload fonts using the <link rel=”preload”> tag in the <head> of your HTML:
<head>
<link rel="preload" href="my-font.woff2" as="font" type="font/woff2"
crossorigin>
</head>Best Practices for Preloading:
Loading fonts from a third-party service, like Google Fonts, can introduce additional network requests and potential delays. Host it on your server or CDN.
Optimizing your fonts is a critical, yet often overlooked, aspect of website performance. By choosing web-safe fallbacks, subsetting your fonts, using font display: swap; (or optional in some cases), and preloading critical fonts, you can significantly reduce font file sizes, improve rendering speed, and create a better user experience. These techniques work together to ensure that your fonts are loaded efficiently and don’t negatively impact your website’s performance. Remember to test your changes and monitor your page speed metrics to ensure your optimizations are effective.
