# What Are Core Web Vitals? LCP, INP and CLS Explained

Source: https://dijitulwebdesign.co.uk/guides/what-are-core-web-vitals/
Updated: 2026-10-18

> Core Web Vitals are Google's three measures of real-world page experience: Largest Contentful Paint for loading, Interaction to Next Paint for responsiveness, and Cumulative Layout Shift for visual stability. dijitul's Business websites, from £500 + VAT, include speed optimisation to pass Core Web Vitals as standard.

## Key facts

- Good LCP: 2.5 seconds or less (web.dev, Google)
- Good INP: 200 milliseconds or less (web.dev)
- Good CLS: 0.1 or less (web.dev)
- Measured at the 75th percentile of real visits, split by mobile and desktop
- INP replaced First Input Delay as a Core Web Vital in 2024
- Check them in PageSpeed Insights and the Core Web Vitals report in Search Console

## The three metrics and their thresholds

| Metric | What it measures | Good (web.dev) |

| Largest Contentful Paint (LCP) | How long until the biggest image or text block in view has loaded | 2.5 seconds or less |
| Interaction to Next Paint (INP) | How quickly the page responds visually after a tap, click or key press | 200 milliseconds or less |
| Cumulative Layout Shift (CLS) | How much content jumps around while loading | 0.1 or less |

Google's web.dev guidance says to assess each metric at the 75th percentile of page loads, segmented by mobile and desktop. So a page passes when at least three quarters of real visits hit the good threshold. INP became a stable Core Web Vital in 2024, replacing First Input Delay.

## Why they matter to a small business

Core Web Vitals are part of how Google assesses page experience, but they are not a magic ranking switch. Relevant, helpful content matters more. Where they really count is with people. A slow page on a phone loses visitors before they see your phone number. A button that jumps as an advert loads causes mis-taps. A menu that takes half a second to open feels broken. Fixing these usually means more enquiries from the same traffic.

They also show where a site's build is weak. A page that fails LCP on mobile is usually carrying oversized images or slow hosting. Poor INP usually points to too much JavaScript. High CLS usually means missing image dimensions or late-loading banners. Each points to a specific, fixable cause rather than a vague sense that the site feels slow.

## How to check your scores

- **PageSpeed Insights** (pagespeed.web.dev): enter a URL. The top section shows field data from real Chrome users if Google has enough; the lower section is a lab test.
- **Search Console**: the Core Web Vitals report groups your URLs into good, needs improvement and poor, for mobile and desktop.
- **Chrome DevTools**: the Performance panel shows which element is your LCP and what causes layout shifts.

Low-traffic sites often have no field data. In that case, use the lab results as a guide and test on a mid-range phone.

Remember that field data covers the previous 28 days, so after you fix something it takes a few weeks for the improvement to show in PageSpeed Insights and Search Console. Use the lab test to confirm the fix straight away, then watch the field data catch up.

## Common causes and fixes

### Slow LCP

- Huge hero images. Resize, compress and serve WebP or AVIF with srcset.
- Lazy-loading the hero image. Only lazy-load images below the fold; give the LCP image fetchpriority='high'.
- Slow hosting or no caching. Server response time adds directly to LCP. See hosting explained.
- Render-blocking CSS, fonts and scripts loaded in the head.

### Poor INP

- Heavy JavaScript from page builders, sliders and chat widgets.
- Too many third-party tags: trackers, heatmaps, social embeds. Remove the ones nobody looks at.

### High CLS

- Images and embeds without width and height set.
- Cookie banners, adverts or notices that push content down after load.
- Web fonts swapping in with very different sizes.

## Platform notes

On WordPress, heavy page builders and stacks of plugins are the usual culprits; a lean theme and a caching setup make a big difference. On Shopify, apps inject scripts into every page, so audit installed apps regularly. Website builders vary; some give limited control over scripts and image handling. A fast, well-built custom theme on any platform will beat a bloated one. See what is a CMS for platform trade-offs.

Whichever platform you use, measure before and after each change, one change at a time, so you know what made the difference.

## When to call us

Our Business package, from £500 + VAT, includes speed optimisation to pass Core Web Vitals. If you want an existing site fixed instead, we can look at the causes and quote, or work at £45 an hour + VAT. Get in touch or call 01623 650333.

## FAQs

### What is a good Core Web Vitals score?

Google's web.dev guidance sets good as Largest Contentful Paint of 2.5 seconds or less, Interaction to Next Paint of 200 milliseconds or less, and Cumulative Layout Shift of 0.1 or less, measured at the 75th percentile of real page loads on mobile and desktop.

### Do Core Web Vitals affect Google rankings?

They are part of Google's page experience signals, but relevance and helpful content carry more weight. Treat them as a way to stop losing visitors to slow, jumpy pages rather than as a shortcut to page one.

### What replaced First Input Delay?

Interaction to Next Paint (INP) replaced First Input Delay as a Core Web Vital in 2024. INP looks at the responsiveness of interactions throughout a visit, not just the first one, so it is a stricter test of how a page feels to use.

### Why does PageSpeed Insights show different scores each time?

The lab test runs on a simulated device and network, so results vary between runs. The field data at the top, from real Chrome users over 28 days, is steadier and is what Core Web Vitals assessment is based on.

### Can a WordPress site pass Core Web Vitals?

Yes. Use a lean theme, avoid heavy page builders where possible, keep plugins to what you need, serve compressed modern images, use caching and decent hosting. Many slow WordPress sites are slow because of what was added to them, not WordPress itself.

## Prices and contact

Prices (from, + VAT): Starter £250 (Up to 5 pages, Custom design, not a template, Mobile-first build, Contact form and click-to-call, Google Business Profile set up, Basic SEO foundations, Analytics and Search Console); Business £500 (Up to 15 pages, A page per service, written to rank, Copywriting included, Full schema markup, Local SEO groundwork, Speed optimised to pass Core Web Vitals, Conversion tracking configured, Training session and recorded walkthrough); Ecommerce £750 (Shopify or WooCommerce, Product and category structure built to rank, Payments and delivery rules configured, Click-and-collect and local delivery, Accounts or EPOS integration, Google Merchant Centre feed, Abandoned cart recovery, Staff training on order management); changes £45 an hour. All prices are "from" and exclude VAT. Every project gets a fixed quote before work starts. Domain registration, stock photography, premium plugins or apps and hosting are listed in the quote, never added later. You own the website and the domain. Aftercare: Hosting from £1 a day + VAT (https://dijihost.co.uk/); Website care plans from £25 a month + VAT (https://dijitulsupport.co.uk/). Contact: https://dijitulwebdesign.co.uk/contact/ · 01623 650333 · info@dijitul.uk