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Large Cumulative Layout Shift (CLS): Elements shifting position unexpectedly during page load or interaction can be disruptive for users. |
Avoid dynamically injected content, reserve space for images and ads, and optimize font loading to minimize CLS. Use the size attribute for images and set explicit dimensions for media elements. |
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Slow Largest Contentful Paint (LCP): Delay in rendering the largest content element on the page affects perceived loading speed. |
Optimize server response times, defer non-essential JavaScript, and prioritize loading critical resources. Use lazy loading for images and optimize image sizes to improve LCP. |
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Poor First Input Delay (FID): Delay in responsiveness to user interactions, such as clicks or taps, can frustrate users. |
Minimize JavaScript execution time, defer non-critical scripts, and optimize third-party scripts. Use browser caching and preconnect/preload resources to reduce network latency and improve FID. |
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Slow Time to First Byte (TTFB): Long TTFB delays the start of page rendering and impacts overall loading speed. |
Optimize server configurations, use content delivery networks (CDNs) to reduce latency, and enable server-side caching. Minimize redirects and optimize database queries to improve TTFB. |
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High Server Response Times: Slow server response times prolong the loading process and degrade user experience. |
Upgrade hosting infrastructure, optimize backend code and database queries, and implement caching mechanisms. Monitor server performance regularly and address bottlenecks promptly. |
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Large JavaScript Bundle Size: Bloated JavaScript files increase download times and execution overhead, affecting performance. |
Split large JavaScript bundles into smaller chunks and lazy-load non-essential scripts. Minify and compress JavaScript files, remove unused code, and utilize code splitting and tree shaking techniques. |
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Inefficient CSS Delivery: Large CSS files and render-blocking stylesheets delay page rendering and increase load times. |
Minimize and optimize CSS files, remove unused styles, and leverage CSS preprocessors for efficient code generation. Inline critical CSS or defer non-critical styles to improve rendering performance. |
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Unoptimized Images: Large image file sizes slow down page loading and increase bandwidth usage. |
Compress and optimize images using appropriate formats (e.g., WebP, JPEG) and compression techniques. Serve responsive images based on device capabilities and viewport size to reduce unnecessary downloads. |
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Render-Blocking Resources: Render-blocking resources, such as JavaScript and CSS files, delay page rendering and increase loading times. |
Minimize the use of render-blocking resources, defer non-critical scripts, and utilize asynchronous loading techniques. Optimize resource loading order and prioritize critical above-the-fold content. |
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Poor Cache Policy: Lack of caching or improper cache policies result in unnecessary resource fetches and slower page loads. |
Implement browser caching for static assets, set appropriate cache-control headers, and utilize service workers for offline caching and background fetching. Leverage CDNs for efficient content delivery and caching. |