Page speed and performance directly influence both search ranking signals and user behavior; this checklist focuses on the diagnostic steps and fixes that have the biggest measurable impact on Core Web Vitals, Time to First Byte, and overall user experience. Use lab tools for repeatable tests and field data for real-world validation.
Gather lab and field data: Lighthouse, WebPageTest, and a real-user measurement source for Core Web Vitals. Capture First Contentful Paint (FCP), Largest Contentful Paint (LCP), Cumulative Layout Shift (CLS), and First Input Delay (FID) or Interaction to Next Paint (INP) where supported. Baseline metrics help prioritize and quantify improvements.
Start at the origin. Reduce Time to First Byte by optimizing server configuration, upgrading hosting, or leveraging an edge CDN. Use HTTP/2 or HTTP/3 where possible and enable TLS session resumption. Confirm keep-alive and compression settings are appropriate. A fast origin reduces latency for uncached content and improves overall responsiveness.
Implement aggressive caching for static assets and set appropriate cache-control headers. Use content hashes on filenames to enable long cache lifetimes. Serve assets from a geographically distributed CDN to reduce latency. For critical assets, consider preloading or using resource hints (preconnect, dns-prefetch) to improve early fetch times.
Minimize render-blocking CSS and JavaScript. Inline critical CSS for above-the-fold content and defer non-critical styles. Split CSS per template if feasible to avoid shipping large global styles to every page. Remove unused CSS via tooling and ensure styles are loaded efficiently to reduce LCP delays.
Audit scripts to identify heavy bundles and third-party scripts that delay interactivity. Defer or async non-essential scripts, split bundles, and adopt code-splitting or server-side rendering for complex interactive features. For sites using large client frameworks, consider partial hydration or progressive enhancement techniques to reduce initial load cost.
Convert images to modern formats like WebP or AVIF where supported, and serve appropriately sized images via responsive srcset or picture elements. Use lazy loading for offscreen images and prioritize hero images for preloading. Optimize encoding and ensure images are not unnecessarily large or duplicated across pages.
Self-host fonts where possible to control caching and delivery. Use font-display swap to avoid invisible text and consider limiting the number of font variants loaded. Preload critical font files and subset fonts to cut download sizes and reduce FOIT/FOUC risks that contribute to CLS or perceived slowness.
Third-party tags (analytics, ads, widgets) are common speed drains. Audit tag performance and move non-essential tags to after-interaction or defer their initialization. For analytics, consider server-side tagging or batched transmissions to reduce client-side impact. Keep a prioritized list of third-party vendors and their measured performance cost.
Cumulative Layout Shift is often caused by images without dimensions, late-loading ads, or dynamic content injection. Ensure width and height attributes are present or use aspect-ratio CSS. Reserve space for ads and embeds and avoid inserting content above existing content unless it is user-initiated. Test on slow networks to emulate worst-case layout shifts.
Integrate performance checks into CI and release pipelines. Run automated Lighthouse or WebPageTest checks for key templates on each release and compare against baseline metrics. Flag regressions early and require fixes for large regressions to prevent production slowdowns from accumulating over time.
Since most users are on mobile networks, prioritize mobile performance. Test on simulated 3G/4G throttling and low-end device profiles. Optimize images and layout for smaller viewports and reduce CPU overhead by minimizing heavy JavaScript tasks. Mobile performance improvements often yield the biggest SEO and conversion gains.
Enable HTTP/2 or HTTP/3 and use a CDN.
Compress and cache assets with long TTLs and hashed filenames.
Defer non-critical JavaScript and inline critical CSS.
Convert images to modern formats and implement responsive images.
Audit and reduce third-party script usage.
Reserve space for dynamically injected content to prevent CLS.
Integrate automated performance tests into deployment pipelines.
Performance optimization is iterative: measure, prioritize, implement, and re-measure. Focus first on pages with the highest traffic and conversion potential. Use a combination of server, asset, and client-side fixes to achieve sustainable improvements that benefit both users and search engines.