What are Core Web Vitals?

Core Web Vitals are three metrics Google uses to measure real-world page experience: Largest Contentful Paint (loading speed), Cumulative Layout Shift (visual stability), and Interaction to Next Paint (responsiveness).

How are Core Web Vitals scored?

Google PageSpeed Insights scores pages 0-100. Above 90 is good, 50-89 needs improvement, and below 50 is poor.

Do Core Web Vitals affect Google rankings?

Yes. Google uses Core Web Vitals as a ranking signal. Pages with good vitals may rank higher when content quality is equal between competitors.

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How to Improve Core Web Vitals Scores

speed Feb 20, 2026 2 min read

What the Core Web Vitals check tests

SiteCurl queries the Google PageSpeed Insights API for your site and reports the performance score along with individual metrics: Largest Contentful Paint (LCP), Cumulative Layout Shift (CLS), Total Blocking Time (TBT), and First Contentful Paint (FCP).

A score of 90+ is good. Between 50 and 89 needs improvement. Below 50 is poor.

Why it matters

Core Web Vitals are a Google ranking signal. Pages that load faster, respond quicker, and stay visually stable rank better and convert more visitors. A one-second delay in LCP can reduce conversions by 7%.

How to fix it

Largest Contentful Paint (LCP)

LCP measures how long it takes for the biggest visible element (usually a hero image or heading) to appear. Target: under 2.5 seconds.

Optimize images: Compress with WebP or AVIF format. Add width and height attributes. Use loading="lazy" for below-the-fold images.
Preload the hero image: <link rel="preload" as="image" href="/hero.webp">
Remove render-blocking resources: Defer non-critical CSS and JavaScript.
Use a CDN: Serve assets from edge locations close to your visitors.

Cumulative Layout Shift (CLS)

CLS measures how much the page layout jumps around while loading. Target: under 0.1.

Set dimensions on images and videos: Always include width and height attributes so the browser reserves space before the file loads.
Avoid inserting content above existing content: Banners, cookie notices, and late-loading ads push content down.
Use font-display: swap: Prevents invisible text while web fonts load.

Total Blocking Time (TBT)

TBT measures how long the main thread is blocked by long JavaScript tasks. Target: under 200ms.

Reduce JavaScript: Remove unused scripts. Split large bundles.
Defer third-party scripts: Load analytics and chat widgets after the page is interactive.
Break up long tasks: Split work into smaller chunks using requestIdleCallback or web workers.

How to verify the fix

Run a SiteCurl scan to see your updated score. You can also check Google PageSpeed Insights directly and look at the Core Web Vitals section in Google Search Console for field data.

Core Web Vitals are closely tied to image optimization, render-blocking resources, and cache headers. Fix those first for the biggest score improvement.

Start a free trial to track your Core Web Vitals over time.