Our Web Performance Audit Playbook: The First 10 Things We Check

Performance audits can go in a hundred directions. Without structure, you spend hours measuring things that do not matter. Our ten-item checklist has identified the primary bottleneck in forty-three out of fifty audits.

Check one: unoptimized images. Accounts for 35 percent of problems. Symptoms: slow load despite fast TTFB, large LCP values. Fix: WebP/AVIF conversion, responsive srcset, lazy-loading below the fold. We have seen LCP drop from four seconds to one from this alone.

Check two: excessive JavaScript bundles. Open coverage tool. Below 60 percent utilization means significant dead code. Common culprits: full lodash imports, charting libraries on chartless pages, render-blocking marketing scripts.

Check three: render-blocking resources. Check the waterfall for CSS and JS blocking initial render. Common: Google Fonts taking 300ms. Fix: self-host fonts, inline critical CSS, defer the rest.

Check four: server response time. TTFB exceeding 600ms points server-side. Trace to slow database queries, external API calls, or missing caching.

Check five: third-party scripts. Count third-party domains. Marketing teams pile on analytics, chat widgets, heatmaps, and retargeting. We regularly find fifteen to twenty scripts adding two to three seconds collectively. Audit, remove unused, lazy-load non-critical, load async.

Check six: layout shifts. Run Lighthouse for CLS. Usually caused by images without dimensions, dynamically injected content, or font reflow. Fix: explicit width/height, placeholder space, font-display swap.

Check seven: database query performance. Enable query logging, look for N+1 queries, missing indexes, overly broad fetches.

Check eight: caching headers. Surprisingly many apps serve hashed static assets with no-cache. Set one-year cache with content hashing for automatic busting.

Check nine: API response payload size. Check if endpoints return fifty fields when five are displayed. Implement field selection or dedicated list endpoints.

Check ten: connection count. Browsers limit concurrent connections per domain. Thirty requests during load creates a waterfall. Use HTTP/2, bundle requests, preload critical resources.

Checks one through five identify the bottleneck about 80 percent of the time. Full checklist takes two to three hours.