Web fonts can significantly impact the user experience of a website, particularly when it comes to cumulative layout shift. Cumulative layout shift occurs when the layout of a webpage shifts during loading, causing elements to move around and affecting the user's ability to interact with the page. Web fonts can contribute to this shift if not optimized properly, leading to a poor user experience and potentially negative SEO implications.
Understanding Cumulative Layout Shift
Cumulative layout shift is measured by the browser and takes into account the amount of time it takes for the page to become stable and the amount of layout shift that occurs during loading. A high cumulative layout shift score can indicate that the page is taking too long to load or that the layout is shifting significantly during loading.
Causes of Cumulative Layout Shift
There are several causes of cumulative layout shift, including:
- Images and videos that are not properly sized or formatted
- Web fonts that are not optimized for loading
- JavaScript files that are not properly loaded or executed
- CSS styles that are not properly applied or loaded
Optimizing Web Fonts for Cumulative Layout Shift
To optimize web fonts for cumulative layout shift, it's essential to use font loading strategies that allow the browser to load fonts before the page is rendered. This can include using font preloading, asynchronous loading, and font compression.
Font Loading Strategies
Font preloading involves loading the font files before the page is rendered, allowing the browser to cache the fonts and reduce the amount of time it takes for the page to become stable. Asynchronous loading involves loading the font files in the background, allowing the page to render without waiting for the fonts to load.
Font Preloading Example
<link rel="preload" href="font.woff2" as="font" type="font/woff2" crossorigin>
Asynchronous Loading Example
const font = new FontFace('My Font', 'url(font.woff2)');
font.load().then(() => {
document.fonts.add(font);
});
Font Compression
Font compression involves reducing the size of the font files to improve page load times and reduce cumulative layout shift. Tools like svg-optimizer can help with font compression by reducing the size of the font files without affecting their quality.
Comparison of Font Formats
The following table compares the different font formats and their characteristics:
| Font Format | Compression | Browser Support | | --- | --- | --- | | WOFF2 | High | Modern browsers | | WOFF | Medium | Most browsers | | TTF | Low | Older browsers | | OTF | Low | Older browsers |
Practical Next Steps
To optimize your web fonts for cumulative layout shift, start by using font loading strategies like font preloading and asynchronous loading. Compress your font files using tools like svg-optimizer to reduce their size and improve page load times. By taking these steps, you can improve the user experience of your website and reduce the negative impacts of cumulative layout shift. Try using the jpg-compressor tool to compress your images and further improve your page load times.