🔴 Critical — Fix before launch · 🟡 Important — Fix if possible · 🟢 Optional — Nice to have

Slow websites lose users before they read a single word. Google also uses Core Web Vitals as a ranking signal. Every millisecond of improvement raises both rankings and conversion rates. This section covers every performance layer from loading to interactivity to infrastructure.

⏱️ Core Web Vitals

💡 Why this group matters: Google measures these 3 signals to determine how good your page experience is. They directly affect both your SEO ranking and how many users stick around.

Largest Contentful Paint (LCP) 🔴 Critical

LCP measures how long it takes for the biggest visible element on screen — hero image, headline, product screenshot — to fully appear. It's when users feel the page has actually loaded.

🎯 Benchmarks: ✅ Under 2.5s — Good · ⚠️ 2.5–4s — Needs work · ❌ Over 4s — Poor

• [ ] LCP is under 2.5s on homepage — tested with PageSpeed Insights
• [ ] LCP is under 2.5s on pricing page
• [ ] LCP is under 2.5s on all primary landing pages
• [ ] LCP is under 2.5s on mobile for all above pages (test mobile separately)
• [ ] Hero/banner image is compressed and served in WebP or AVIF format
• [ ] Hero image has fetchpriority="high" attribute set so browser downloads it first
• [ ] Hero image is NOT lazy-loaded — lazy loading the LCP image significantly hurts the score
• [ ] Server response time (TTFB) is under 600ms — check in PageSpeed Insights "Server response times" audit
• [ ] Critical above-the-fold CSS is inlined in the HTML head or preloaded
• [ ] Render-blocking scripts are deferred or moved to end of body
• [ ] Web fonts are preloaded or using font-display: swap to avoid blocking render

📌 Diagnose: PageSpeed Insights → scroll to "LCP element" — it shows exactly what's slow and why