Caching web fonts with the JavaScript Cache API

23 Oct 2023

Web fonts are an essential part of modern web design, but they can also have a negative impact on performance. Each time a web page is loaded, the browser has to download the web fonts used in that page, which can cause delays in rendering the text and overall loading speed. One way to improve performance is by caching web fonts using the JavaScript Cache API.

What is the Cache API?

The Cache API is a web API that provides a way to store and retrieve responses from a server or network in the browser’s cache. It allows developers to control what resources are stored in the cache and how they are retrieved. By caching web fonts, we can reduce the number of network requests needed to load a web page and improve the performance of the website.

Caching Web Fonts

To cache web fonts using the Cache API, we need to follow these steps:

Register a service worker: Service workers are JavaScript files that run in the background and can intercept network requests. We need to register a service worker in our web page to handle caching of web fonts.

if ('serviceWorker' in navigator) {
  navigator.serviceWorker.register('/service-worker.js')
    .then(function(registration) {
      console.log('Service worker registered with scope:', registration.scope);
    })
    .catch(function(error) {
      console.log('Service worker registration failed:', error);
    });
}

Intercept font requests: In the service worker file (service-worker.js), we can intercept network requests for web fonts and cache the responses.

self.addEventListener('fetch', function(event) {
  if (event.request.url.endsWith('.woff') || event.request.url.endsWith('.woff2')) {
    event.respondWith(
      caches.match(event.request).then(function(response) {
        if (response) {
          return response;
        }
        return fetch(event.request).then(function(networkResponse) {
          caches.open('web-fonts').then(function(cache) {
            cache.put(event.request, networkResponse.clone());
          });
          return networkResponse;
        });
      })
    );
  }
});

Store web fonts in the cache: When we intercept a font request, we first check if the font exists in the cache. If it does, we return the cached response. If it doesn’t, we fetch the font from the network, store it in the cache, and then return the network response.
Retrieve web fonts from the cache: When a web page requests a web font, the service worker intercepts the request and checks if the font is in the cache. If it is, the cached response is returned, reducing the need to download the font from the network.

Benefits of Caching Web Fonts

By caching web fonts using the Cache API, we can achieve several benefits:

Improved performance: Caching web fonts reduces the number of requests and the time required to load fonts, resulting in faster page loading overall.
Offline availability: Once the web fonts are cached, they can be accessed and displayed even when the user is offline or the network is slow.
Bandwidth savings: Caching web fonts reduces the amount of data transfer required, resulting in lower bandwidth usage for the website and potentially reducing costs for users.

Conclusion

Caching web fonts using the JavaScript Cache API is a powerful technique to improve website performance, especially in scenarios where web fonts are used extensively. By reducing the number of network requests and ensuring offline availability, web fonts can be loaded faster and provide a better user experience. Consider implementing this caching strategy to optimize your web fonts and enhance your website’s speed and performance.

References:

#webfonts #webperformance