Performance Engineering Tool

Core Web Vitals & Speed Checklist

The definitive developer checklist for optimizing LCP, INP, and CLS scores to pass Google PageSpeed Insights.

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1. Largest Contentful Paint (LCP < 2.5s)

Preload Hero Banner & Fonts

Use fetchPriority='high' on main LCP image and next/font/google with font-display: swap.

WebP / AVIF Modern Image Formats

Compress images and use responsive srcSet sizes to avoid loading desktop images on mobile.

Fast Time to First Byte (TTFB < 800ms)

Use static site generation (SSG) or edge caching CDN to serve static HTML instantly.

Defer Heavy Third-Party Scripts

Load non-critical scripts (chatbots, analytics) asynchronously or using requestIdleCallback.

Break Up Long Main-Thread Tasks (> 50ms)

Decompose synchronous JavaScript loops into non-blocking microtasks or Web Workers.

Set Explicit Image Width & Height

Always specify aspect ratio or explicit width and height attributes on <img> and <svg> tags.

Reserve Space for Dynamic Banners

Pre-allocate container min-height for dynamically injected components or banners.

Nexiv Tech builds sub-second Next.js web applications with 98+ Lighthouse performance scores.