I recently updated my website and was surprised by how long the pages take to load. The images are already optimized, and I don't have any unnecessary JavaScript that I know of. I started from a template, though, so the stylesheet still contains some rules and components I may not need. Could an oversized CSS file be responsible for most of the slowdown? I'm looking for a tool or workflow that can identify the specific files or requests causing the delay.
3 Answers
CSS can delay rendering, but it generally has to be unusually large or complex before it becomes the main problem. Large media files and third-party requests are more common causes. In this case, several GIFs add up to around 9 MB, which is a major amount for a page, so replacing them with more efficient video or image formats would likely help. Mixed HTTP and HTTPS assets should also be fixed.
Run the page through Lighthouse, PageSpeed Insights, or WebPageTest for a more organized report. These tools can point out render-blocking resources, inefficient caching, uncompressed files, oversized media, and other performance issues.
Start with your browser’s developer tools. Open the Network tab, disable the cache, reload the page, and sort requests by size and loading time. That will show whether a particular image, script, stylesheet, font, or third-party request is holding things up. Also check the Console for errors and blocked or insecure requests.
The Network panel is usually enough to find the main culprit because it shows exactly how long each resource takes and whether it is being served efficiently.