Core Web Vitals Explained: Why Your Site Speed Directly Affects Google Rankings

Google ranks websites, not just keywords. One of the things it measures is how fast and smooth your site is to use.

Since 2021, Google has officially used Core Web Vitals as ranking signals. Sites with better scores get a boost. Sites with poor scores get penalised. Here’s what you need to know.

The three Core Web Vitals

1. Largest Contentful Paint (LCP)

What it measures: How long it takes for the largest visible element - usually a hero image or main heading - to load on screen.

Score	Time
Good	Under 2.5 seconds
Needs improvement	2.5–4 seconds
Poor	Over 4 seconds

2. Interaction to Next Paint (INP)

What it measures: How quickly your site responds when someone clicks or taps something - a button, a menu, a form field.

Score	Time
Good	Under 200ms
Needs improvement	200–500ms
Poor	Over 500ms

3. Cumulative Layout Shift (CLS)

What it measures: How much the page layout jumps around while loading. You’ve experienced this: you tap a button, and just as you tap, it shifts down and you hit the wrong thing.

Score	Value
Good	Under 0.1
Needs improvement	0.1–0.25
Poor	Over 0.25

How to check your scores

1. Go to PageSpeed Insights and enter your URL
2. Run the test on Mobile - that’s what Google measures
3. Look at the Core Web Vitals section

A score of 90+ (green) is good. 50–89 (orange) needs improvement. Under 50 (red) is actively hurting your rankings.

The common causes of poor scores

Poor LCP:

• Large, unoptimised images (1 MB+ JPGs)
• Slow web hosting (shared servers, no CDN)
• Render-blocking JavaScript or CSS

Poor INP:

• Too much JavaScript running on page load
• Heavy third-party scripts (chat widgets, ad trackers)

Poor CLS:

• Images without width and height attributes
• Ads or embeds that load after the page content
• Web fonts causing text to shift when they load (FOUT/FOIT)

The fastest fix

The fastest way to pass Core Web Vitals is to use modern infrastructure:

• Static site generator (Astro, Hugo) instead of WordPress
• CDN hosting (Cloudflare Pages) instead of shared servers
• Optimised, compressed images with proper dimensions
• Minimal JavaScript - load only what you need

Sites built with Astro and hosted on Cloudflare Pages consistently score 95–100 on PageSpeed Insights without any special optimisation. The architecture does the work for you.

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