Page speed metrics meet thresholds

Lighthouse Performance score below 80 on desktop or 60 on mobile indicates a page is delivering a measurably degraded experience relative to the performance budget Google uses for crawl prioritization. FCP above 1.8s means users see a blank screen for a full second longer than acceptable — search engines track this as a proxy for content delivery quality. TBT above 300ms indicates long JavaScript tasks blocking the main thread, which delays interactivity and degrades INP. iso-25010:2011 performance-efficiency.time-behaviour is the relevant quality dimension — these are engineering thresholds, not aspirational targets.

Run npx lighthouse https://yoursite.com --preset=desktop and --preset=mobile to baseline your scores. Target the two highest-TBT contributors first — usually large JavaScript bundles and third-party scripts.

In next.config.js, enable compression and restrict bundle output:

// next.config.js
module.exports = {
  compress: true,
  images: { formats: ['image/avif', 'image/webp'] },
  experimental: { optimizePackageImports: ['lucide-react', 'date-fns'] },
}

For third-party scripts causing TBT, switch to next/script with strategy="lazyOnload" in app/layout.tsx. For FCP, inline critical CSS and defer non-critical stylesheets. Re-run Lighthouse after each change — don't batch optimizations, as individual impact is hard to attribute otherwise.