Serving site assets, such as images, stylesheets, and JavaScript files, from multiple domains has become a common practice for optimizing web performance.
This technique, known as domain sharding, involves distributing site assets across multiple domains to take advantage of the browser's parallel loading capabilities. In this article, we will explore why it has become better to serve site assets from multiple domains and how it can improve web performance.
Browser's parallel loading capabilities
The primary reason for using domain sharding is to take advantage of the browser's parallel loading capabilities. Browsers are designed to download a limited number of assets from a single domain in parallel. This means that if a web page has a large number of assets, the browser will queue the downloads and wait for each asset to be downloaded before moving on to the next. This can result in slow loading times and a poor user experience.
By serving site assets from multiple domains, developers can increase the number of assets that can be downloaded in parallel, reducing the time it takes for the page to load. For example, if a site has 20 assets, the browser may only download 4 assets in parallel from a single domain. By serving these assets from 2 domains, the browser can download 8 assets in parallel, reducing the time it takes for the page to load.
Impact of slow-loading assets
Another reason for using domain sharding is to reduce the impact of slow-loading assets. When an asset is slow to load, it can slow down the entire page and affect the user experience. By serving site assets from multiple domains, developers can reduce the impact of slow-loading assets by ensuring that other assets can continue to load in parallel.
Additionally, domain sharding can help to reduce the amount of data that needs to be transferred over the network. When assets are served from multiple domains, the browser can reuse cached assets from previous visits to the site, reducing the amount of data that needs to be transferred. This can result in faster load times and a better user experience.
It is important to note that domain sharding is not a silver bullet for improving web performance. While it can provide some benefits, it also has some potential drawbacks. For example, creating and maintaining multiple domains can be time-consuming and costly, and it can also increase the complexity of the site's infrastructure. Additionally, some browsers may limit the number of parallel connections to a single domain, negating the benefits of domain sharding.
In conclusion, serving site assets from multiple domains can provide several benefits for optimizing web performance. By taking advantage of the browser's parallel loading capabilities and reducing the impact of slow-loading assets, domain sharding can result in faster load times and a better user experience. However, it is important to weigh the potential benefits against the costs and potential drawbacks before implementing domain sharding on a site.