Quick answer: Core Web Vitals are three Google metrics that measure real visitors' experience: Largest Contentful Paint (LCP) for loading speed, Interaction to Next Paint (INP) for responsiveness, and Cumulative Layout Shift (CLS) for visual stability. Good scores are LCP of 2.5 seconds or less, INP of 200 milliseconds or less, and CLS of 0.1 or less, measured at the 75th percentile of page visits. They are a ranking factor, but their bigger impact is on conversions: slow, jumpy pages lose visitors.
The three Core Web Vitals
| Metric | What it measures | Good | Needs improvement | Poor |
|---|---|---|---|---|
| LCP | How fast the main content appears | ≤ 2.5 s | 2.5–4 s | > 4 s |
| INP | How quickly the page responds to taps and clicks | ≤ 200 ms | 200–500 ms | > 500 ms |
| CLS | How much the layout jumps while loading | ≤ 0.1 | 0.1–0.25 | > 0.25 |
INP replaced the older First Input Delay (FID) metric in March 2024, because it measures responsiveness across the whole visit, not just the first interaction.
Largest Contentful Paint (LCP)
LCP marks the moment the biggest visible element, usually a hero image or headline, finishes loading. Visitors judge speed by it. Common causes of slow LCP are large hero images, slow hosting, render-blocking CSS and JavaScript, and web fonts that load late.
Interaction to Next Paint (INP)
INP measures the delay between a tap or click and the next visual update. A poor INP feels like a page that ignores you. It is usually caused by heavy JavaScript: large themes, page builders, chat widgets, tracking scripts and sliders.
Cumulative Layout Shift (CLS)
CLS measures unexpected movement. You have experienced it when you try to tap a button and an ad or image pushes it down at the last moment. It is caused by images without dimensions, late-loading banners and fonts that swap size.
Do Core Web Vitals affect SEO?
Yes, as part of Google's page experience signals, but they are not the most important ranking factor. Relevance and quality of content matter more. Think of Core Web Vitals as a tiebreaker in search and a major factor in conversions.
Why speed matters more for sales than for rankings
Visitors do not wait. Every extra second on a slow mobile connection gives people a reason to go back to the search results and pick a competitor. A fast, stable page also feels more professional and trustworthy, which supports every other conversion element on the page.
How to check your Core Web Vitals
- Google Search Console: the Core Web Vitals report groups your URLs by status, using real Chrome user data.
- PageSpeed Insights: shows field data from real visitors (when available) and lab data with specific suggestions.
- Chrome DevTools Lighthouse: useful for testing changes before you publish.
Field data from real visitors is what counts for Google. Lab scores are a diagnostic tool, not the goal.
How to improve LCP
- Compress and resize the hero image. Use WebP or AVIF and serve the size the screen needs.
- Preload the hero image and give it high fetch priority.
- Do not lazy-load the main image at the top of the page.
- Use fast hosting and caching, and a CDN for global audiences.
- Reduce render-blocking CSS and JavaScript.
- Self-host fonts and use
font-display: swap.
How to improve INP
- Remove scripts you do not need, especially unused plugins and widgets.
- Delay third-party scripts such as chat and heatmaps until after the page is interactive.
- Avoid heavy page builders and sliders where a simpler layout would do.
- Break up long JavaScript tasks if you have custom code.
How to improve CLS
- Set width and height on every image and video.
- Reserve space for banners, embeds and ads.
- Avoid inserting content above existing content after the page loads.
- Use font fallbacks with similar sizes to your web fonts.
What about WordPress and page builders?
WordPress sites can be fast, but themes and page builders often add a lot of code. The biggest wins usually come from removing unused plugins, using a lightweight theme, optimizing images and adding good caching. If a site is fundamentally slow because of its build, a rebuild can be cheaper than endless patching. Our website redesign checklist explains how to do that without losing rankings.
Frequently asked questions
What are good Core Web Vitals scores?
LCP of 2.5 seconds or less, INP of 200 milliseconds or less and CLS of 0.1 or less, measured at the 75th percentile of real page visits.
Why is my PageSpeed score different every time?
Lab tests depend on network and server conditions at that moment, so scores vary. Focus on field data in Search Console, which reflects real visitors over 28 days.
How long until Google sees my speed improvements?
Field data is based on a rolling 28-day window, so improvements show up gradually over about four weeks.
A fast website is part of every web design project and website care plan we deliver. Want to know what is slowing your site down?
