Remove unused CSS and JavaScript: see what each page loads but never uses

Enter the page above: Chromium loads it with code coverage on and lists every script and stylesheet by unused bytes, first party and third party apart, with Google's estimate of the time you would save. In Chrome itself, open developer tools, press Ctrl+Shift+P (Cmd+Shift+P on a Mac), run Show Coverage and reload the page.

Because most sites ship one stylesheet for every page: the rules for checkout, the blog, sliders and every theme option load on the home page too. Frameworks such as Bootstrap and page builders add many rules a page never uses. It matters most when the file blocks rendering, so inline the CSS the first screen needs and load or trim the rest.

Yes, more than unused CSS byte for byte, because the browser downloads, parses and compiles every script while the main thread is busy. That delays the first render when scripts block it, and makes the page slower to respond to taps, which shows in INP. Load scripts with defer, split them by page and drop libraries you no longer use.

Most unused code on a WordPress page comes from plugins and page builders that load their files everywhere. Use your cache or performance plugin's options to delay JavaScript and remove unused CSS, turn on your builder's own asset-loading settings, and unload plugin files on pages that do not need them. The report also shows each plugin's cost and the builder's share.

Rarely all of it. Most code unused on one page is used elsewhere: on another template, after a click, in the checkout. The fix is to load each piece only where it is needed. A theme that ships one giant stylesheet for every page is the classic case: 80 to 95 percent unused on any single page is normal, and splitting it often saves more than any other speed change.

We use the same coverage data, but count characters of decoded code during load and settle only, on one page load without clicks. The Coverage tab in DevTools keeps counting while you click around, so its unused share goes down as you use the page. Both are right; ours shows what the first visit downloads but does not need.

Files from another company's domain, such as tag managers, chat widgets, video embeds and ad scripts. You cannot shrink them yourself, only decide whether they load and when. Delay the ones visitors rarely use until they interact, and drop those nobody looks at; they often cost more main-thread time than your own code.