A route-level performance baseline
Review available field Core Web Vitals separately from reproducible lab traces, grouped by representative template and device. Use TTFB and FCP as diagnostic timings where useful; they are not Core Web Vitals.
Core Web Vitals
I connect each performance symptom to the browser and application work behind it, distinguish user-facing metrics from diagnostic timings, and prioritize changes that fit the product.
Discuss your projectDiagnose loading, interaction, and visual stability across important routes using field and lab evidence where available. Trace bottlenecks through fonts, images, CSS, JavaScript bundles, third-party scripts, hydration, and server work.
Review available field Core Web Vitals separately from reproducible lab traces, grouped by representative template and device. Use TTFB and FCP as diagnostic timings where useful; they are not Core Web Vitals.
Trace LCP, INP, or CLS symptoms to likely causes such as server work, hydration and main-thread JavaScript, bundle and CSS cost, font/image loading, third-party scripts, or unstable layout. Implement agreed fixes or provide a prioritized engineering plan.
Repeat the same lab journeys and, when enough field data exists, monitor the relevant user groups after release. Record test conditions and remaining bottlenecks; do not treat one Lighthouse score as field performance.
Agree on representative URLs, devices, user actions, and the field data that best reflects the experience.
Use browser traces and code inspection to separate server response, rendering/hydration, resource priority, CSS/layout, fonts/images, bundles, and third-party work.
Make focused changes and compare under the same device, route, and lab conditions. Review field data only when it exists and has adequate coverage; document trade-offs and follow-on work.
No. Scores vary by device, network, traffic, and test conditions. I focus on repeatable improvements to representative user journeys and field signals.
Yes, when available. Field data helps establish how users experience the site; lab tests help isolate causes and compare changes.
No. Next.js is a common context, but the same diagnosis and optimization approach applies to other web stacks.
Have a defined brief, or just a stubborn problem?