If it takes more than ten seconds to load a web page, even the best content won’t keep visitors around. We’ve recently reviewed quite a few websites and found that many of them load slowly; the problem often isn’t the web page itself, but rather that the resources it relies on haven’t been properly optimized.
The process of loading a web page generally goes like this: The browser first fetches the HTML page, parses it, and then requests files such as JavaScript, CSS, and images based on the page content, ultimately rendering the page. Therefore, the main factors affecting display speed are the size and number of these auxiliary resources; optimizing their loading will naturally make the page load faster.
The following seven methods are all approaches we frequently use in real-world projects and that yield quick results:
- Optimize Image Formats and Sizes: Images are typically the most space-consuming resources on a page. While ensuring display quality, try to use formats with higher compression rates whenever possible; you can prioritize them in the following order: WebP > JPEG > PNG > BMP. Also, load images at the size corresponding to their actual display dimensions—do not use the original images directly. We’ve encountered situations where a 196×196 display slot had an image file that was several megabytes in size; upon investigation, we discovered that the original 1960×1960 image had been uploaded directly.
- Enable gzip compression. When a browser requests a web page, it includes a header such as `Accept-Encoding: gzip` to indicate support for compressed transmission. If gzip is enabled on the server, text-based resources can typically reduce data transfer by 70% to 80%, resulting in a significant improvement in loading speed.
- Using Browser Caching: Different pages on the same website typically reuse a set of shared resources, such as CSS, JavaScript, and images. By configuring these files to be cacheable, users won’t need to retrieve them from the server again when they refresh the page or navigate to another page, which naturally results in much faster loading times.
- Reduce Redirects: Some websites use different domain names for different devices, causing visitors to be redirected before the page loads. Each redirect forces the browser to send a new request, unnecessarily increasing wait times. Instead, it’s better to use responsive design so that a single site can accommodate all devices.
- Distributing Static Resources via a CDN: A CDN caches static content on nodes located in various regions. When users access the content, it is automatically retrieved from the node closest to them, which significantly reduces the distance the resources must travel. Images, CSS, JavaScript, and other elements on a webpage are generally static content, making them ideal for hosting on a CDN.
- Reduce the Number of DNS Lookups If the resources on a page are spread across multiple domain names, the browser must resolve each domain name individually, and each resolution takes time. Consolidating static resources, such as images, under a single domain name to reduce DNS lookups is a low-cost yet highly effective optimization technique.
- Compressing CSS and JS is different from Step 2. While gzip compression occurs at the transport layer, this step involves removing unnecessary spaces and line breaks from CSS and JS files and shortening variable names to reduce file size at the source, which in turn speeds up loading times.
To summarize the seven points above, there are three key takeaways: reduce the number of requests, minimize resource size, and shorten the distance resources travel. If your website hasn’t undergone these optimizations yet, you might want to review it and make the necessary changes—once you do, you’ll see a noticeable improvement in loading performance.
