Core Web Vitals: What Google Measures & Why It Matters

Three Numbers That Determine Where You Rank

Before Google ranks your page, it measures three things about the experience of loading and using it. These three measurements are called Core Web Vitals — and they are confirmed Google ranking signals for every website.

Most business owners have never heard of them. Most of their websites are failing them.

According to HTTP Archive’s 2025 Web Almanac data, only 46% of websites pass all three Core Web Vitals on mobile. That means more than half of the web — your industry, your competitors, your market — is sitting in the “Needs Improvement” or “Poor” category on Google’s own scoring system.

The Three Metrics, Precisely Defined

LCP — Largest Contentful Paint (Loading Speed)

What it measures: How long it takes for the largest visible element on the page — typically a hero image, headline, or video — to fully render after a user navigates to the page.

Google’s thresholds:

• Good: Under 2.5 seconds
• Needs Improvement: 2.5–4 seconds
• Poor: Over 4 seconds

Why it matters: LCP is the metric most directly correlated with whether a user stays or leaves. If the main content takes more than 4 seconds to appear, most mobile users have already made their judgment and left.

INP — Interaction to Next Paint (Responsiveness)

What it measures: How quickly the page responds to every user interaction — every click, tap, and key press — throughout the entire session. INP replaced FID (First Input Delay) in March 2024 as the responsiveness metric in Core Web Vitals.

Google’s thresholds:

• Good: Under 200 milliseconds
• Needs Improvement: 200–500 milliseconds
• Poor: Over 500 milliseconds

Why it matters: A page that loads fast but freezes when you click a button fails INP. Heavy JavaScript — the kind generated by bloated WordPress plugins and third-party scripts — is the primary cause of poor INP scores.

CLS — Cumulative Layout Shift (Visual Stability)

What it measures: How much the page layout unexpectedly shifts while loading. When images, ads, or embeds load without reserved space, they push content down — causing users to click the wrong element, lose their reading position, or register accidental taps.

Google’s thresholds:

• Good: Under 0.1
• Needs Improvement: 0.1–0.25
• Poor: Over 0.25

Why it matters: Poor CLS directly causes user frustration and misclicks. For any page with a booking form, contact button, or purchase flow, unexpected layout shifts cost real conversions.

What ‘Passing’ Actually Means

To pass Core Web Vitals, 75% of real-world page visits must meet the “Good” threshold for all three metrics simultaneously — measured from actual Chrome user data, not just lab tests.

This is a high bar. It is not enough to pass in a developer’s clean test environment. The measurement comes from real users on real devices and real connections.

The CMS Performance Gap

The 2025 HTTP Archive Web Almanac provides the most authoritative benchmark of Core Web Vitals performance across platforms:

CMS Platform	Mobile CWV Pass Rate
Duda	85%
TYPO3	79%
Wix	74%
Drupal	63%
Joomla	57%
WordPress	46%

WordPress sits last among major CMS platforms — 39 percentage points behind Duda. The cause is architectural: WordPress loads PHP on every request, relies heavily on plugins that inject bloated JavaScript, and has no built-in edge caching by default.

Static-first architectures — like the Astro + Cloudflare stack we use — serve pre-built HTML directly from a global edge network, eliminating the database queries, PHP execution, and plugin overhead that drag WordPress performance down.

Why This Directly Affects Your Revenue

Core Web Vitals are not an abstract technical score. They map directly to user behavior and business outcomes.

web.dev’s business optimization guide documents consistent patterns across industry case studies: improving Core Web Vitals correlates with measurable reductions in bounce rate, increases in session duration, and conversion rate improvements. For local businesses competing on similar services and pricing, page experience is often the tiebreaker between ranking on page one and ranking on page two.

A page on page two of Google receives approximately 0.63% of clicks. A page on page one position three receives approximately 10%. The difference between a passing and failing Core Web Vitals score — all other content being equal — can determine which side of that divide you sit on.

Related Reading

Core Web Vitals scores are a direct product of how your website is built. Read how our Astro + Cloudflare stack achieves 90+ PageSpeed scores by design and why we moved away from WordPress. For the business impact of speed at a fundamental level, see Speed is Revenue: The ROI of Milliseconds.

References

1. Google Search Central: Understanding Core Web Vitals and Google Search Results
2. web.dev: Core Web Vitals — The Official Metrics
3. web.dev: Optimize Core Web Vitals for Business Decision Makers
4. HTTP Archive: 2025 Web Almanac — CMS Chapter