Font loading can make or break your website’s performance. Slow-loading fonts lead to poor user experience, delayed content visibility, and even lower SEO rankings. Here’s how to fix it:
- Use Modern Formats: Switch to WOFF2 for smaller file sizes and quicker loads. It’s supported by 97% of browsers.
- Prevent FOIT/FOUT: Use the
font-displayproperty (swap,optional) to avoid invisible or unstyled text flashes. - Self-Host Fonts: Gain full control over performance and privacy by hosting fonts yourself instead of relying on third-party services.
- Subset Fonts: Remove unused characters to shrink file sizes and speed up downloads.
- Preload Fonts: Use
<link rel="preload">to prioritize font loading and improve rendering speed. - Variable Fonts: Combine multiple styles into one file to reduce HTTP requests and improve flexibility.
Quick Comparison of Font Loading Strategies
| Strategy | Benefit | Drawback |
|---|---|---|
| WOFF2 Format | Smaller file size | Requires browser support |
| Self-Hosting | Full control, better privacy | Requires technical setup |
| Font-Display | Avoids invisible text | May cause layout shifts |
| Preloading | Speeds up loading | Requires manual setup |
| Variable Fonts | Fewer requests, flexible | Larger initial file size |
Start by combining these techniques for faster, more consistent font loading. This ensures better user experience and improved Core Web Vitals scores.
Font Loading Performance: 6 Experiments with FOUT & FOIT
Font Selection and Preparation
Choosing the right fonts and preparing them properly can improve website performance and reduce loading times.
Web Font Types and Formats
Among web font formats, WOFF2 stands out for its excellent compression. With 97% browser support , it offers substantial file size reductions. For instance, Intel’s ClearSans font saw a 25% decrease in size when converted to WOFF2 .
| Format | Compression | Browser Support | Best Use Case |
|---|---|---|---|
| WOFF2 | 30–60% smaller | 97% | Ideal for modern browsers |
| WOFF | Standard compression | Widely supported | Backup for older browsers |
| TTF/OTF | No compression | Limited | Desktop use or development |
| EOT | Basic compression | Internet Explorer only | Legacy support |
"Webfonts are critical to good design, UX, and performance." – Ilya Grigorik, Web Performance Engineer at Google
To make these formats even more efficient, focus on reducing file sizes through subsetting and compression.
Font File Size Reduction
Minimizing font file sizes is key to faster page loads. Subsetting – keeping only the characters you need – helps reduce downloads without sacrificing quality.
Modern compression techniques also make a big difference:
- WOFF2’s Brotli compression delivers 26.61% better ratios compared to WOFF1 .
- Tools like pyftsubset can remove unused characters effectively .
- Additional compression using GZIP or Brotli further trims file sizes .
"Each font is an additional resource, and some fonts may block rendering of the text, but just because the page is using WebFonts doesn’t mean that it has to render slower." – Ilya Grigorik
These steps ensure your fonts are optimized and ready for hosting, whether self-hosted or through third-party services.
Font Hosting Options
Once your fonts are optimized, you’ll need to decide between self-hosting and using third-party services. Each option has its pros and cons, depending on your priorities for performance, control, and privacy. For example, over 45% of the top 10,000 websites use Google Fonts , but self-hosting is becoming more popular due to privacy and performance benefits.
| Feature | Self-Hosting | Third-Party Services |
|---|---|---|
| Performance | Better with a proper CDN | Depends on service reliability |
| Control | Full control over optimization | Limited customization |
| Privacy | Stronger GDPR compliance | Possible privacy issues |
| Setup Complexity | Requires technical skills | Easy to implement |
| Font Selection | Unlimited options | Restricted to service library |
The Web Almanac 2022 highlights: "there is no longer a performance benefit to using a hosted service after the introduction of cache partitioning, meaning that now self-hosting web fonts is universally recommended."
To maximize performance when self-hosting:
- Use a CDN for global distribution.
- Leverage HTTP/2 for faster delivery.
- Set up proper caching headers.
- Implement preconnect to speed up connections .
Font Loading Methods
Efficient font loading is key to improving web performance. Let’s break down some practical methods to ensure your fonts load quickly and effectively.
Font Preloading Setup
Using link rel='preload' helps prioritize font downloads, speeding up load times. When added to the <head> section of your HTML, this method ensures fonts are ready when needed.
Here’s how to set it up:
<link rel="preload" href="path/to/your/font.woff2" as="font" type="font/woff2" crossorigin>
Three attributes make this work smoothly:
| Attribute | Value | Purpose |
|---|---|---|
| as | "font" |
Tells the browser it’s a font |
| type | "font/woff2" |
Specifies the font’s MIME type |
| crossorigin | "" |
Ensures CORS compliance |
"The
preloadvalue of the element’s rel attribute lets you declare fetch requests in the HTML’s, specifying resources that your page will need very soon, which you want to start loading early in the page lifecycle, before browsers’ main rendering machinery kicks in." – MDN Web Docs
Once preloading is set, you can fine-tune how fonts render on the page.
Font Display Settings
The font-display property helps manage font rendering, reducing issues like FOIT (Flash of Invisible Text) or FOUT (Flash of Unstyled Text). Each setting offers different benefits:
| Setting | Block Period | Best For | Use Case |
|---|---|---|---|
| swap | 0ms | Body text | Prioritize content visibility |
| optional | 100ms | Decorative fonts | Performance-critical pages |
| fallback | 100ms | Secondary content | Balance speed and style |
| block | 2–3s | Critical branding | Brand-focused elements |
"If you don’t know which option to use, go with
swap. It allows you to use custom fonts and tip your hand to accessibility. If you use fonts that are ‘nice to have’, but could ultimately do without, consider specifyingoptional." – Jeremy Wagner
For more complex needs, JavaScript-based font loading offers additional precision.
Loading Fonts with JavaScript
JavaScript provides more control over how fonts are loaded, making it ideal for advanced scenarios or when working with third-party font providers. This approach allows for adaptive loading based on user settings and helps reduce layout shifts.
For the best results, consider combining CSS font-display with JavaScript. This hybrid method balances simplicity with flexibility, especially when dealing with fonts from external services that might not fully support CSS-only solutions.
sbb-itb-608da6a
Advanced Font Loading Techniques
Optimizing font loading on complex websites can dramatically improve performance. Techniques like using variable fonts and smart loading strategies can make a big difference.
Using Variable Fonts
Variable fonts combine multiple styles into a single file, cutting down on HTTP requests and speeding up load times. These fonts operate through axes of variation – like weight, width, or slant – giving designers a wide range of options without needing separate files for each style.
| Aspect | Static Fonts | Variable Fonts |
|---|---|---|
| File Size | Around 20KB per variation | Single file (e.g., ~3.36MB for Roboto) |
| Design Flexibility | Limited to preset styles | Offers multiple variations |
| Animation Support | Not supported | Fully supported |
| Performance Impact | Requires multiple HTTP requests | Single request with better caching |
By reducing file requests and improving caching, variable fonts help create a smoother browsing experience. Adding fallback strategies ensures users don’t experience visual hiccups during loading.
Font Fallback Settings
Fallback fonts are crucial for maintaining a polished look while custom fonts load. Matching the metrics of system and custom fonts can minimize layout shifts. Tools like @capsizecss/core generate CSS that aligns text metrics, making transitions seamless. For instance, Vercel’s next/font automatically uses the size-adjust property based on the actual font files (e.g., .ttf or .woff2), ensuring smooth switches between fallback and custom fonts.
Delayed Font Loading
Another way to optimize performance is by delaying non-critical font loads. Using font-display: optional allows fallback text to render immediately while custom fonts load in the background.
Here’s how to implement it effectively:
- Use
font-display: optionalfor instant fallback rendering. - Subset fonts to include only the characters you need.
- Replace icon fonts with SVGs for better performance and accessibility.
This method ensures fonts load efficiently without compromising the user experience, keeping your site fast and visually consistent.
Font Performance Testing
Evaluate font loading performance using specific metrics to pinpoint issues. Effective testing helps maintain quick load times and ensures smooth user experiences.
Font Loading Metrics
Here are key metrics to assess font performance:
| Metric | Description | Impact |
|---|---|---|
| FOUT (Flash of Unstyled Text) | Displays text in a fallback font before the custom font loads. | Can cause visual shifts, affecting user perception. |
| FOIT (Flash of Invisible Text) | Keeps text hidden until the custom font loads. | Reduces perceived performance if loading takes too long. |
| CLS (Cumulative Layout Shift) | Measures visual stability during page load. | Directly affects Google’s Core Web Vitals score. |
Font Testing Tools
-
Lighthouse: Available in Chrome DevTools, Lighthouse provides detailed font loading audits. It flags FOIT problems and suggests fixes. You can use Lighthouse through:
- Chrome DevTools
- A standalone Chrome extension
- A Node.js module for automated testing
- WebPageTest: This tool offers detailed insights with frame-by-frame video capture, custom performance markers, and testing across various devices and locations .
These tools help you consistently monitor font performance and address any issues.
Regular Performance Checks
Incorporate these checks into your workflow:
- Routine Audits: Use tools like Google PageSpeed Insights to monitor font-related metrics.
- Browser Cache Settings: Ensure proper caching headers are applied to font files.
- Font Optimization: Reduce file sizes by subsetting custom fonts and limiting their use .
Balancing quick content display with visual stability is crucial for delivering a smooth experience across devices and network conditions.
Next, we’ll dive into actionable steps to implement these insights effectively.
Font Loading Guidelines
Modern font loading is all about finding the right balance between speed and aesthetics. Here’s how to optimize your website’s font delivery while avoiding common mistakes.
Step-by-Step Font Loading
-
Choose and Prepare Fonts
Stick to WOFF2 format for the best compression and performance . -
Configure Font Display Settings
Adjust thefont-displayproperty to match your site’s needs:Strategy Ideal For Drawbacks Optional Speed-focused websites Custom fonts might not appear Swap Branding-critical fonts Possible layout shifts Fallback Balanced priorities Short swap period -
Optimize Font Loading
- Self-host fonts for better control.
- Use resource hints like
preconnectto speed up connections. - Inline critical font declarations within the
<head>for faster initial rendering .
With these steps, your fonts will load efficiently without compromising on appearance.
Font Loading Mistakes to Avoid
Here are some common errors that can slow your site:
- Too Many Font Families: Limit yourself to two font families to keep load times quick .
- Outdated Formats: Skip obsolete formats and stick with WOFF2 for smaller file sizes .
- Text Rendering Delays: Be aware of browser behavior – Chromium and Firefox delay text rendering for up to 3 seconds if fonts aren’t loaded, while Safari may block text indefinitely .
Advanced Font Loading Techniques
Take your font performance to the next level with these methods:
- Variable Fonts: Use them with size adjustment descriptors for smoother visual transitions.
size-adjustDescriptor: Add this to your@font-facerules to reduce visual disruptions during font swaps .- Subsetting Tools: Tools like subfont and glyphhanger can strip out unused glyphs, reducing file sizes .
Interestingly, websites using third-party fonts sometimes see faster rendering than those relying entirely on first-party fonts .
Summary and Action Steps
Main Points Review
Optimizing font loading is all about finding the right balance between speed and design. Here are some key strategies:
| Strategy | Benefit | Complexity |
|---|---|---|
| WOFF2 Format | Compresses fonts 30% more than WOFF | Easy |
| Self-hosting | Gives you more control over loading | Medium |
| Font Subsetting | Cuts down file size by removing unused characters | Medium |
| System Fonts | Loads instantly with no delay | Easy |
Start by using modern formats like WOFF2 and cutting unnecessary font weights. These simple steps can lead to noticeable improvements. For more advanced solutions, professional expertise might be the next step.
Getting Expert Help
Sometimes, optimizing fonts can get tricky, especially if you’re dealing with:
- Ongoing Core Web Vitals issues tied to fonts
- Complex typography setups for multiple languages
- Inconsistent font rendering across devices
If that sounds familiar, it might be time to bring in the pros. For example, OneNine specializes in web performance optimization, offering services like advanced font loading strategies, performance monitoring, and audits. They use tools such as Google PageSpeed Insights and WebPageTest to measure and improve font performance.
Another example is NitroPack‘s 2023 Font Subsetting case study, which shows how expert-level optimization can enhance both Core Web Vitals and user experience.
