Core Web Vitals 2025 Checklist for Founders

TL;DR: Core Web Vitals are Google's official speed and user experience metrics that directly affect your search rankings. Three main metrics: LCP (how fast your page looks loaded), INP (how responsive it feels to clicks), and CLS (how stable the layout is). This checklist tells you what they mean, how to test them for free, and exactly what to ask your developer to fix.

You keep hearing "Core Web Vitals" in conversations about SEO and website performance. Your developer mentions it. Your SEO consultant brings it up. And every time, you nod along while quietly wondering what it actually means.

This guide is for you.

No jargon. No code. Just a clear explanation of what Core Web Vitals are, why they matter for your business, and a concrete checklist your team can act on today.

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What Are Core Web Vitals?#

Core Web Vitals are three specific measurements Google uses to score how good your website feels to use — from a real user's perspective.

Google introduced them as ranking factors in 2021 and has refined them since. In 2025, they remain one of the clearest, most actionable signals in Google's ranking algorithm.

Here's the key insight: Google doesn't just want to send people to the page with the best content. It wants to send people to the page with the best content that also loads fast, responds instantly, and doesn't jump around while loading.

If two pages are equally relevant for a search query, the one with better Core Web Vitals scores will rank higher. That's the direct business case.

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The Three Core Web Vitals (2025)#

1. LCP — Largest Contentful Paint#

What it is: How long it takes for the largest visible element on your page to fully load.

That "largest element" is usually your hero image, a big headline, or a product photo. It's the thing that makes the page feel "done" to a visitor.

Why it matters: If a visitor lands on your page and the main content doesn't appear for 4 seconds, many of them leave. LCP measures exactly that experience.

The scoring:

Plain English translation: Your page's main content should appear within 2.5 seconds. If it takes longer, you're losing visitors and search rankings.

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2. INP — Interaction to Next Paint#

What it is: How fast your page responds when a user clicks a button, opens a menu, or types in a form.

INP replaced the older FID (First Input Delay) metric as of March 2024. It measures the worst interaction delay across the full time a user spends on your page — not just the first click.

Why it matters: A page that looks fast but freezes when you click a button is a terrible experience. JavaScript-heavy websites often have high INP because the browser is busy running scripts instead of responding to user actions.

The scoring:

Plain English translation: When someone clicks something on your site, the page should visually respond within 200 milliseconds. That's 0.2 seconds. If it takes longer, the site feels sluggish and broken.

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3. CLS — Cumulative Layout Shift#

What it is: How much your page layout unexpectedly moves around while it loads.

You've experienced this: you're about to click a button and suddenly an ad loads above it, pushing everything down. You accidentally click the wrong thing. That is a layout shift — and CLS measures how much of this happens on your page.

Why it matters: Layout shifts are frustrating. They cause accidental clicks, make content hard to read, and signal to Google that your page experience is poor.

The scoring:

Plain English translation: The lower the CLS score, the more stable your page. Aim for 0.1 or below. Zero is perfect.

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Why Core Web Vitals Matter for Your Business (The Numbers)#

These aren't abstract technical metrics. Here's what the data shows:

• Amazon calculated that every 100ms of additional load time cost them 1% in sales
• Google's own research shows that pages loading in 1-3 seconds have a 32% higher bounce rate than pages loading under 1 second — and pages loading in 1-5 seconds have a 90% higher bounce rate
• Sites that pass Core Web Vitals thresholds see on average 24% fewer page abandonments (Google, 2020)
• For e-commerce specifically, a 0.1-second improvement in mobile page speed can increase conversion rates by 8% (Deloitte, 2020)

Put simply: a slower website with worse Core Web Vitals means fewer visitors, higher bounce rates, and fewer conversions — regardless of how good your product or content is.

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How to Test Your Core Web Vitals Right Now (Free)#

You can test your site's Core Web Vitals in the next 5 minutes with these free tools:

Tool 1: PageSpeed Insights#

URL: pagespeed.web.dev

Enter your URL. Get scores for both mobile and desktop. This is the official Google tool — use it first.

Key things to look at:

• The "Field Data" section (real user data from Chrome users, if available)
• The "Lab Data" section (simulated test)
• The "Opportunities" section — this tells you exactly what to fix

Tool 2: Google Search Console#

URL: search.google.com/search-console

If you have Search Console set up (you should — it's free), navigate to "Experience → Core Web Vitals" in the left sidebar. This shows your real-world scores across all your pages, based on actual user visits over 28 days.

This is the most important data source because it reflects real user experience, not simulated tests.

Tool 3: Chrome DevTools Lighthouse#

In Chrome, open DevTools (F12 or Cmd+Option+I), go to the "Lighthouse" tab, and run a Performance audit. This gives you a detailed breakdown with specific, actionable recommendations.

Tool 4: web.dev/measure#

URL: web.dev/measure

Similar to PageSpeed Insights but with a slightly more readable report format. Good for sharing results with non-technical stakeholders.

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The Core Web Vitals Fix Checklist#

Use this checklist to identify and address issues. Share it with your developer and ask them to work through each item.

LCP Fixes (Loading Speed)#

• Optimise your hero image — Compress it, convert to WebP format, and make sure it's the right dimensions (no 4000px-wide image displayed at 800px)
• Add loading="eager" and fetchpriority="high" to your LCP image — This tells the browser to load it first
• Remove render-blocking resources — JavaScript and CSS that load in the <head> before content can appear
• Enable a CDN — Cloudflare (free tier) or similar so assets load from a server physically close to the visitor
• Check your server response time (TTFB) — If Time to First Byte is over 800ms, your hosting or server-side code is the bottleneck
• Use next/image (if on Next.js) — Handles WebP conversion, lazy loading, and correct sizing automatically

INP Fixes (Interactivity)#

• Audit third-party scripts — Chat widgets, tag managers, marketing pixels, and analytics scripts all add JavaScript that blocks the main thread. Remove or defer anything non-essential
• Break up long JavaScript tasks — Any JavaScript function taking more than 50ms blocks the browser's ability to respond to clicks. Ask your developer to identify "long tasks" in the Performance tab of Chrome DevTools
• Defer non-critical JavaScript — Use defer or async attributes on script tags, or lazy-load components that aren't needed immediately
• Reduce JavaScript bundle size — Use code splitting so only the code needed for the current page is loaded. Next.js does this automatically if configured correctly

CLS Fixes (Layout Stability)#

• Set explicit width and height on all images — Without these, the browser doesn't know how much space to reserve, causing shifts when images load
• Set explicit dimensions for ad slots and embeds — Ads, YouTube videos, and iframes that load late cause layout shifts unless you reserve their space in advance
• Avoid inserting content above existing content — Cookie banners, notification bars, and promotional pop-ups that appear at the top of the page push content down (layout shift). Load them with reserved space or at the bottom
• Use font-display: optional or font-display: swap for web fonts — Fonts that load late cause text to "jump" when they replace the fallback font
• Test with Chrome DevTools Layout Shift Regions — In DevTools → Rendering → enable "Layout Shift Regions" to visually see where shifts happen

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A Practical Priority Order#

If you're facing a long list of issues and need to prioritise, work in this order:

Priority 1: LCP on mobile Mobile traffic is the majority for most websites, and mobile LCP is almost always worse than desktop. Fix your hero image, enable a CDN, and reduce render-blocking resources first.

Priority 2: CLS CLS fixes are usually quick and have high impact. Adding image dimensions and reserving space for ads and banners can dramatically improve your score in a single afternoon.

Priority 3: INP INP fixes are more technical — they require JavaScript profiling and optimisation. Start by identifying and removing unnecessary third-party scripts (a non-technical fix), then pass the detailed work to your developer.

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What "Good" Core Web Vitals Looks Like in Practice#

Here is a real example of the kind of work I do at dipanshudev.com:

A client's website had an LCP of 6.8 seconds on mobile. The culprit: a 1.2MB hero image served as a PNG, no CDN, and three third-party chat/analytics scripts loading synchronously in the <head>.

After:

• Converting the hero to WebP at 40% quality (visually identical, 85% smaller)
• Adding fetchpriority="high" to the hero image tag
• Moving the analytics and chat scripts to load after the page content
• Enabling Cloudflare CDN

Result: LCP dropped to 1.9 seconds. CLS went from 0.22 to 0.04. The site passed all three Core Web Vitals thresholds.

The entire fix took one working day.

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Core Web Vitals and Technical SEO Together#

Core Web Vitals are part of a broader set of signals Google calls the Page Experience signals. These include:

• Core Web Vitals (LCP, INP, CLS)
• HTTPS (secure connection)
• No intrusive interstitials (no full-screen pop-ups blocking content)
• Mobile-friendliness

At dipanshudev.com/services, every new website build includes a full Page Experience audit as part of the technical SEO setup — because there's no point ranking on page one if your site loads poorly and users bounce immediately.

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The Quick-Reference Scorecard#

Print this, share it with your developer, or paste it into your next project brief:

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Summary#

Core Web Vitals are not a developer concern — they're a business concern. They affect your Google rankings, your visitor experience, and your conversion rate. Every millisecond of load time and every layout shift is costing you traffic and leads.

The good news: most Core Web Vitals issues are fixable. They don't require a full website rebuild — they require specific, targeted fixes that a competent developer can implement in days, not months.

Test your site today at pagespeed.web.dev. Note your scores. Share this checklist with whoever manages your website. Then act on it.

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