Site Speed Test.
Core Web Vitals. Waterfall. Suggestions. In one scan.
Paste a URL and we'll run a full Lighthouse + WebPageTest hybrid scan — LCP, INP, CLS, full waterfall, render-blocking resources, and the three highest-impact fixes — all in about 30 seconds.
Bookmark-worthy moments.
Four moments when speed isn't a vanity metric — it's the difference between conversion and bounce.
Run a pre-launch performance audit
Before a marketing site goes live, scan every key page. Catch the 4MB hero image, the render-blocking analytics script, the third-party widget that shoves your LCP to 5 seconds.
Catch a regression after a deploy
Engineering shipped something on Tuesday. Wednesday morning, LCP is up 800ms. Run the scan, find the new JS bundle, ship the fix before anyone files a ticket.
Benchmark against competitors
Run your top 3 competitors through the same scan. Compare LCP, INP, CLS side by side. If they're consistently faster, you have a competitive disadvantage you can fix in two sprints.
Diagnose a single slow page
PMs say a specific landing page feels slow. Run it through the waterfall, see exactly which resource is the long tall bar, kill or defer it.
What are Core Web Vitals, really?
The three metrics Google actually uses to rank your page experience — explained without the jargon.
Core Web Vitals are the three performance metrics Google has officially codified as part of its ranking signal. They replaced the older, hand-wavy 'page experience' bucket with concrete, measurable numbers. If your site is in the 'poor' bucket for any of them on a meaningful share of traffic, Google deprioritizes you in ranking — and your users feel it before any algorithm does.
LCP (Largest Contentful Paint) measures how long the biggest visible element takes to render. Under 2.5s is good; over 4s is poor. INP (Interaction to Next Paint) replaced FID in 2024 and measures input responsiveness — how long it takes the browser to respond after a click or tap. Under 200ms is good; over 500ms is poor. CLS (Cumulative Layout Shift) measures visual stability — how much elements jump around as the page loads. Under 0.1 is good; over 0.25 is poor.
This tool runs the same Lighthouse-based scan Google uses, plus a parallel WebPageTest waterfall so you can see not just what's slow but why. Each scan returns the three highest-impact fixes, ranked by estimated improvement in milliseconds.
Core Web Vitals · quick reference
Largest Contentful Paint — when the biggest above-the-fold element finishes rendering.
Good < 2.5sInteraction to Next Paint — responsiveness after the worst input the user makes.
Good < 200msCumulative Layout Shift — how much elements jump around during loading.
Good < 0.1Time To First Byte — how long the server takes to start responding.
Good < 800msFirst Contentful Paint — when any content first appears on screen.
Good < 1.8sTotal Blocking Time — how long the main thread is blocked during load (lab metric).
Good < 200msField = real user data (CrUX). Lab = synthetic test (this tool). Field is what Google ranks on.
Both reportedAsked. Answered.
Tool questions, topic questions — answered without the hedging. Anything missing? Email hi@seonova.io and we'll fold it in.
Both, in parallel. Lighthouse gives the score-based audit; WebPageTest gives the detailed network waterfall. We merge them into one view so you don't have to run two tools.
More to bookmark.
Tools that share the same engine — and tend to land in the same tab group.
Monitor speed across every page, every day.
SEONova Pro runs this scan across every URL you own daily, tracks field vs lab divergence, and pages on-call when LCP or INP cross your threshold. The free tool catches problems. The platform catches them before users do.