What are Core Web Vitals?

Core Web Vitals are three Google signals that measure the real-world experience of a web page: Largest Contentful Paint, which is how fast the main content appears; Cumulative Layout Shift, which is how much the layout moves around while loading; and Interaction to Next Paint, which is how quickly the page responds when someone taps or clicks. Stackra reports all three in plain business language.

Why are my mobile scores worse than desktop?

Phones have slower processors and network connections than laptops, so the same page often performs worse on mobile than on desktop. Because most visitors arrive on a phone, Stackra shows the mobile results first and measures mobile and desktop separately so you see the experience that matters most.

Does Time to First Byte count toward Core Web Vitals?

No. Time to First Byte is how long your server takes to start responding. Stackra shows it as helpful background context about your hosting, but it is a diagnostic value only and does not count toward your Core Web Vitals result or score.

What is a good LCP, CLS, and INP score?

As a guide, Largest Contentful Paint is good at 2.5 seconds or less, Cumulative Layout Shift is good at 0.1 or less, and Interaction to Next Paint is good at 200 milliseconds or less. Values above these thresholds mean visitors are starting to feel the page is slow, jumpy, or unresponsive.

Core Web Vitals Checker

See how fast and stable your pages really feel, on mobile and desktop, with each score explained in plain business terms.

This is one slice of the full scan

A full Stackra scan adds a Growth Readiness Score, expert AI reviews, and a prioritized action plan across your whole site.

How the Core Web Vitals Checker works

Stackra measures three Google signals for the real-world experience of your page: how fast the main content appears (LCP), how stable the layout is while it loads (CLS), and how quickly the page responds to taps and clicks (INP). We report mobile and desktop separately, because most visitors arrive on a phone.

Why do mobile and desktop scores differ?

Phones have slower processors and connections than laptops, so the same page often performs worse on mobile. Since most visitors are on mobile, we show that view first.

Is Time to First Byte part of the score?

No. We show TTFB as helpful background context about your server, but it is a diagnostic value only and does not count toward your Core Web Vitals result.

How do Core Web Vitals affect my business?

Slow or unstable pages make visitors leave before they convert, and they are a ranking factor in Google. Faster, steadier pages keep more people on the page and improve search visibility.

What counts as a good Core Web Vitals score?

Google's thresholds: LCP (how fast the main content loads) should be under 2.5 seconds. CLS (layout shift while loading) should be under 0.1. FCP (first content on screen) should be under 1.8 seconds. Scores in the "needs improvement" band still rank, but they cost you visitors who leave before the page finishes loading. The mobile score is what matters most, since the majority of web traffic arrives on phones.

Why do so many WordPress sites fail Core Web Vitals?

Plugin bloat is the primary cause. WordPress's flexibility means sites accumulate scripts, stylesheets, and page builders over time, each adding load time. Based on Chrome field data, about 48% of WordPress sites pass all three Core Web Vitals on mobile. Shopify sites pass at around 78%, largely because the platform controls the rendering stack and limits what merchants can add. If you are on WordPress and failing, the fastest wins are usually image optimization, removing unused plugins, and switching to a caching or performance plugin.

Source: HTTP Archive / CrUX Technology Report, February 2026.

What is the fastest thing I can fix?

For most sites, the biggest LCP gains come from image optimization: compressing images, converting to WebP, and adding a width and height attribute so the browser reserves space before the image loads. If your host is slow (high TTFB), upgrading to a CDN-backed host or adding server-side caching is the next lever. Both changes typically cost nothing or very little and show up in field data within two to four weeks.

Related guides and checklists

Keep going with hands-on guides and a checklist you can work through on your own site.

Small Business SEO Audit ChecklistFree checklist, no agency jargon.How to Read Google PageSpeed Insights: What the Scores Mean Why Is My Website So Slow? How to Fix It Without a Developer Website Performance Benchmarks: How Does Your Site Compare?