Css are unused style resources still downloaded by browser

Since larger files take longer to download, unused CSS slows down the page load. This is an issue by itself, but it gets even worse when we consider the role CSS plays in constructing the render tree. CSS is responsible for how each page looks, so browsers must load, parse and apply all CSS files referenced in the head tag before rendering the page.  · How to detect unused CSS # The Coverage tab of Chrome DevTools can help you discover critical and uncritical CSS. See View used and unused CSS with the Coverage tab. Chrome DevTools: Coverage tab. You can also extract this information from Puppeteer. See bltadwin.ruge. Inline critical CSS and defer non-critical CSS #.  · Different browsers define it differently. For example, in Firefox, styles applied to the tag are deemed "unused" and thusly, any images won't be downloaded. Chrome 26 (possibly all of them, not sure), does download CSS images if they are applied to the element, even when JS is enabled. (It isn't immediately clear to me why though, perhaps this is a bug?).Reviews: 1.

CSS Critical: The CSS critical (or "above the fold") collects all the CSS used to render the visible portion of the page. It is embedded before your principal CSS call and between stylestyle in a single line (minified if possible). Why: Inlining critical CSS help to speed up the rendering of the web pages reducing the number of. Having unused CSS rules is not a good thing because: Use prefetch if the resource will be used for the next pages, so the resource is downloaded with a low priority. Priority Hints is a new way to inform the browser a resource is important or not. This is only supported by Google Chrome. The Coverage tool gives us data for used versus unused bytes. If your total CSS bytes are small, then the unused percentage becomes less important. For example, my home page is around 57% unused. Because my total CSS is small, my Lighthouse scores are still around Note that it's only accurate for the styles (or scripts) used thus far.

The more unused CSS there is, the more time that a browser might potentially need to spend calculating the styles for each node. How to detect unused CSS # The Coverage tab of Chrome DevTools can help you discover critical and uncritical CSS. See View used and unused CSS with the Coverage tab. Chrome DevTools: Coverage tab. Opera and the Firefox browser have a popular add-on called Dust Me that scans your current web page and lists all the unused CSS rules that are defined in the stylesheet but not used on the page. Google Chrome users however do not need to install any add-ons as the Developer Tools built inside the Google browser itself offer this option. One such source of cruft comes in the form of unused CSS rules which are no longer necessary for the site to function, yet still consume bandwidth. For your convenience, the Unused CSS Rules audit.