Speed Trap

Core Web Vitals & Performance Audit

We don't just give you numbers — we show the top optimization opportunities with estimated millisecond savings. Powered by PageSpeed/Lighthouse lab audits with separate CrUX field data when available.

What We Test

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LCP (Largest Contentful Paint) — time to render largest visible element (good: <2.5s, needs improvement: 2.5-4s, poor: >4s)
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CLS (Cumulative Layout Shift) — visual stability score (good: <0.1, needs improvement: 0.1-0.25, poor: >0.25)
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FCP (First Contentful Paint) — time to first DOM content render (good: <1.8s, needs improvement: 1.8-3s, poor: >3s)
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Speed Index — visual progress metric showing how quickly page content is visually populated
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TBT (Total Blocking Time) — main thread blocking duration preventing user input (good: <200ms, needs improvement: 200-600ms, poor: >600ms)
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TTFB (Time to First Byte) — server response latency (good: <800ms, needs improvement: 800-1800ms, poor: >1800ms)
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Lighthouse performance score — weighted composite lab score (0-100) from mobile and desktop runs
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Optimization opportunities — image optimization, unused JavaScript, render-blocking resources, with millisecond savings estimates
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Lighthouse diagnostics — excessive DOM size, long tasks, unminified assets, legacy JavaScript detection
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CrUX field data (when available) — URL or origin real-user metrics shown separately from lab data
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Secondary scores — Accessibility, Best Practices, SEO category scores for holistic site health

Why Core Web Vitals Impact SEO & Conversion

Google uses Core Web Vitals as ranking and UX signals. Slow LCP means users see a blank page and bounce before content loads. High CLS means buttons and links move while people try to click them. Poor TBT makes the page feel unresponsive. We run Lighthouse lab audits in Chromium, surface optimization opportunities with estimated savings, and show CrUX field data separately when the API provides it. That keeps synthetic lab findings and real-user measurements clearly separated.

Actionable Performance Optimization Fixes

When we detect performance issues, we prioritize fixes by estimated time savings. For slow LCP, we recommend preloading critical resources (fonts, hero images), using CDN for static assets, and implementing server-side rendering or static generation. For high CLS, we suggest reserving space for dynamic content (aspect-ratio boxes for images, skeleton screens), avoiding layout shifts from web fonts (font-display: swap with fallback metrics), and preventing banner injections. For poor TBT, we identify long JavaScript tasks and suggest code splitting, lazy loading non-critical scripts, and deferring third-party analytics. For slow TTFB, we recommend edge caching, database query optimization, and CDN configuration. Every recommendation includes framework-specific implementation patterns and links to Lighthouse documentation.