Core Web Vitals Performance Review Checklist
A performance review checklist built around Core Web Vitals. It covers field measurement, LCP/INP/CLS levers, image and script optimization, delivery, and a CI performance budget.
When to Use This Checklist
Use this checklist to review a web application against Core Web Vitals, Google's user-centric metrics for loading (LCP), interactivity (INP), and visual stability (CLS). Run it before a launch, during a performance push, or whenever field data shows users on slow devices or networks are struggling. Good vitals improve both experience and search ranking.
How to Use This Checklist
Start with field data from real users, not just lab runs, because lab tools miss the device and network diversity that drives real scores. Field data tells you which metric to fix first.
Attack each metric with its known levers. For LCP, optimize the largest element and its critical path. For INP, break up long main-thread tasks and reduce JavaScript work during interactions. For CLS, reserve space for images, ads, and fonts so the page does not jump. Image optimization, code splitting, and font preloading address all three at once.
Third parties and delivery often dominate. Audit external scripts and defer or remove the non-essential ones, then confirm caching, compression, and a CDN are in place. Lock in gains with a performance budget enforced in CI so regressions are caught before release.
What Good Looks Like
Field data shows LCP, INP, and CLS in the good range for most users, including those on low-end devices. The LCP element and critical path are optimized, main-thread work is trimmed, and layout shifts are eliminated. A performance budget runs in CI, and continuous monitoring alerts on regressions.
Common Pitfalls
The most common pitfall is optimizing against lab scores while real users stay slow; only field data reflects reality. Teams often ignore third-party scripts, which can dominate INP and load time. Forgetting to reserve space for dynamic content causes avoidable layout shift. Without a CI performance budget, hard-won gains erode release by release.
Related Resources
Pair this with Google Web Vitals, performance budgets, lazy loading and code splitting, and image optimization. Mobile-first design keeps low-end devices in scope.