Test Your Core Web Vitals
Measure LCP, CLS, FCP, and TBT across every page on your site using Google Lighthouse. SEOAudits identifies performance bottlenecks and gives you specific, actionable fixes to speed up your website.
TL;DR: SEOAudits tests your site's Core Web Vitals (LCP, CLS, FCP, TBT) using Google Lighthouse. Get specific fixes for every performance issue affecting your rankings.
What Are Core Web Vitals?
Core Web Vitals are a set of specific factors that Google considers important in a webpage's overall user experience. They are part of Google's Page Experience signals used for ranking websites in search results.
Introduced in 2020 and fully integrated into Google's ranking algorithm by 2021, Core Web Vitals measure three key aspects of user experience: loading (how fast content appears), interactivity (how quickly the page responds to user input), and visual stability (whether elements shift unexpectedly).
In 2024, Google expanded the Core Web Vitals to include Interaction to Next Paint (INP) as a replacement for First Input Delay (FID). SEOAudits measures all relevant performance metrics including the foundational ones: LCP, CLS, FCP, and TBT.
Why Core Web Vitals Matter for SEO
- Direct ranking factor — Google uses Core Web Vitals as a confirmed ranking signal for mobile and desktop search
- User experience correlation — Sites with good CWV see lower bounce rates and higher conversion rates
- Mobile-first indexing — With mobile-first indexing, mobile performance directly impacts all rankings
- Competitive advantage — Most sites fail CWV tests; fixing yours puts you ahead of competitors
Core Web Vitals Thresholds
Google defines three performance categories for each metric: Good (green), Needs Improvement (orange), and Poor (red). SEOAudits uses these exact thresholds to score your pages.
| Metric | Good | Needs Improvement | Poor |
|---|---|---|---|
LCP Largest Contentful Paint | ≤ 2.5s | 2.5s – 4.0s | > 4.0s |
CLS Cumulative Layout Shift | ≤ 0.1 | 0.1 – 0.25 | > 0.25 |
FCP First Contentful Paint | ≤ 1.8s | 1.8s – 3.0s | > 3.0s |
TBT Total Blocking Time | ≤ 200ms | 200ms – 600ms | > 600ms |
Understanding Each Metric
Largest Contentful Paint
Measures loading performance. LCP marks the point when the largest visible content element (image, video, or text block) is rendered on the screen.
How to Fix
Optimize images (WebP, responsive sizing), use a CDN, preload critical resources, eliminate render-blocking resources, and improve server response time.
Cumulative Layout Shift
Measures visual stability. CLS quantifies how much unexpected layout shift occurs during the entire lifespan of the page. A low CLS means elements do not jump around as the user interacts with the page.
How to Fix
Always include width and height attributes on images and videos, reserve space for dynamically injected content, and avoid inserting content above existing content unless in response to a user interaction.
First Contentful Paint
Measures the time from when the page starts loading to when any part of the page content is rendered on the screen. FCP is a user-centric metric for perceived load speed.
How to Fix
Eliminate render-blocking resources by deferring non-critical CSS and JavaScript, reduce unused CSS, preconnect to required origins, and use a fast hosting provider.
Total Blocking Time
Measures interactivity. TBT quantifies the total amount of time between First Contentful Paint and Time to Interactive where the main thread was blocked for long enough to prevent input responsiveness.
How to Fix
Break up long JavaScript tasks into smaller chunks, defer non-critical JavaScript, minimize main thread work by reducing complex DOM structures, and use Web Workers for heavy computations.
How SEOAudits Tests Core Web Vitals
SEOAudits integrates with Google Lighthouse to measure Core Web Vitals across every page of your website. During the crawl, our worker runs Lighthouse on each page and extracts the four key metrics: LCP, CLS, FCP, and TBT.
These metrics are stored per-page and aggregated into your overall audit score. The Performance category accounts for 20% of your total SEO score, making it one of the most impactful areas to optimize.
For each metric that falls into "Needs Improvement" or "Poor" territory, SEOAudits creates a specific issue in your audit report with the current value, threshold comparison, and step-by-step remediation instructions.
Performance Scoring Breakdown
| Metric Status | Page Score Impact | Severity |
|---|---|---|
| All metrics Good | No penalty | Info |
| LCP Needs Improvement | -10 points | Warning |
| LCP Poor | -20 points | Critical |
| CLS Poor | -15 points | Critical |
| No Lighthouse data | -25 points | Warning |
Frequently Asked Questions
How accurate is SEOAudits's Core Web Vitals measurement?
SEOAudits uses Google Lighthouse for performance measurements, which is the same engine Google uses for Core Web Vitals. Our lab data results are highly accurate and strongly correlate with field data from the Chrome User Experience Report (CrUX).
What is the difference between lab data and field data?
Lab data (what SEOAudits measures) is collected in a controlled environment with predefined settings. Field data comes from real users visiting your site via the Chrome browser. Lab data is consistent and reproducible; field data reflects real-world variability. Both are valuable — lab data helps you debug, field data validates the user experience.
Can I test Core Web Vitals without signing up?
Yes. The free plan includes 1 audit per month with Core Web Vitals testing for up to 25 pages. No credit card required. Sign up with a magic link and run your first audit in under a minute.
How often should I test Core Web Vitals?
We recommend testing Core Web Vitals at least monthly, or after any significant site change (new theme, plugin updates, content migrations). SEOAudits's Pro and Agency plans support scheduled audits that run automatically on a weekly or monthly basis.
Test your site's speed now
Run a free Core Web Vitals test across your entire site and get specific fixes for every performance issue.
Start Free Test