What Is Core Web Vitals and Why Does Google Care?

If you've ever looked at your Google Search Console and seen warnings about "Core Web Vitals", you're not alone. Most business owners see those alerts and have no idea what they mean or why they matter.

Here's the short version: Core Web Vitals are Google's way of measuring how good your website feels to use. If your scores are bad, Google pushes you down the rankings. If they're good, you get a boost. Simple as that.

The three metrics that matter

LCP — Largest Contentful Paint

This measures how long it takes for the biggest visible element on your page to load — usually the hero image, a large heading, or a video thumbnail. Google wants this to happen in under 2.5 seconds.

Why it matters: If your page takes 4+ seconds to show its main content, over half your visitors will leave before they see anything. You're paying for traffic (through SEO or ads) that bounces before it even arrives.

Common causes of bad LCP:

• Massive uncompressed images (the #1 culprit)
• Slow server response time (cheap hosting)
• Render-blocking JavaScript and CSS
• Too many third-party scripts (analytics, chat widgets, fonts)

INP — Interaction to Next Paint

INP replaced the old FID (First Input Delay) metric in 2024. It measures how quickly your site responds when someone interacts with it — clicking a button, tapping a menu, filling in a form.

Why it matters: If someone clicks "Add to Cart" and nothing happens for half a second, they think it's broken. They click again. Maybe they leave. A responsive site feels professional. A laggy site feels amateur.

Common causes of bad INP:

• Heavy JavaScript frameworks doing too much work
• Too many event listeners on the page
• Complex animations running on the main thread
• WordPress sites with 20+ plugins all loading scripts

CLS — Cumulative Layout Shift

Ever been reading a page on your phone, and suddenly the text jumps down because an ad or image loaded above it? That's layout shift. Google measures this and penalises sites that do it.

Why it matters: Layout shift is infuriating for users. It causes misclicks, disrupts reading, and makes your site feel unstable. Google knows this because they track user behaviour at massive scale.

Common causes of bad CLS:

• Images without width and height attributes
• Ads or embeds that load after the page
• Web fonts loading and causing text to reflow
• Dynamically injected content above the fold

How to check your scores

Go to pagespeed.web.dev, enter your URL, and hit analyse. You'll get scores for both mobile and desktop, plus specific recommendations for what to fix.

Pay attention to the mobile score — that's what Google uses for ranking. Desktop is almost always higher because desktop computers are faster than phones.

Score guide:

• 90–100: Excellent — you're in great shape
• 50–89: Needs improvement — you're leaving rankings on the table
• 0–49: Poor — this is actively hurting you

How to fix bad Core Web Vitals

The good news is that most Core Web Vitals issues are fixable without rebuilding your entire site:

• Compress and resize images — use WebP format, size them to the display dimensions
• Upgrade your hosting — cheap shared hosting is often the bottleneck
• Remove unused plugins — every plugin adds JavaScript that slows your site
• Defer non-critical scripts — analytics and chat widgets don't need to load first
• Set image dimensions — always include width and height to prevent layout shift
• Use a CDN — serve assets from servers closer to your visitors

We offer speed optimisation from £150 — we'll fix everything flagged by Google and give you a before/after report.