How to improve the page's first screen time by optimizing the critical rendering path?
When needing to improve the page's first contentful paint time, optimizing the critical rendering path requires focusing on the collaborative optimization of HTML parsing, CSS rendering blocking, and JavaScript execution efficiency. This involves reducing the size of critical resources, adjusting loading order, and eliminating blocking to shorten rendering time. HTML Optimization: Streamline critical HTML code, remove redundant comments and whitespace, and reduce file size using compression tools like Gzip to speed up browser parsing. CSS Handling: Inline critical CSS into the `<head>` to avoid external CSS blocking rendering; load non-critical CSS asynchronously using media queries to reduce interference with first-screen rendering. JavaScript Loading: Use the `async` or `defer` attributes for non-critical JS to prevent blocking HTML parsing; place JS scripts at the bottom of the `<body>` to reduce preemption of first-screen rendering. Resource Prioritization: Preload critical resources such as fonts and CSS using `<link rel="preload">` to ensure the browser优先获取渲染必需文件. It is recommended to use performance tools like Lighthouse to identify blocking resources in the critical rendering path, prioritize optimizing large or delayed-loading CSS/JS files, and achieve effective reduction of first contentful paint time through gradual testing and adjustments.
