Core Web Vitals Explained in Plain English
Core Web Vitals are Google's attempt to measure how a page feels to use rather than how fast a server responds. There are three of them, they are all measurable, and each has a small set of usual causes. Here is what they mean and what to do about them.
The three metrics
LCP — Largest Contentful Paint
How long until the main thing on the page appears. Usually your hero image or headline. It answers the visitor's question: has anything actually loaded? Good is under 2.5 seconds.
INP — Interaction to Next Paint
How quickly the page responds when someone taps or clicks. It replaced First Input Delay in 2024 because FID only measured the first interaction, which flattered pages that got sluggish later. Good is under 200 milliseconds.
CLS — Cumulative Layout Shift
How much the page jumps around while loading. If you have ever tapped a button and hit an ad because the layout moved, that is CLS. Good is under 0.1.
How much do they affect rankings?
They are a genuine ranking signal, but a modest one compared with relevance and content quality. A fast page about the wrong topic will not outrank a slower page that answers the query properly.
Where they matter most is as a tiebreaker between similar pages, and — more importantly — for conversion. Visitors abandon slow pages regardless of how they rank, so the business case for fixing them rarely rests on SEO alone.
Fixing LCP
- Compress and correctly size the hero image — the most common cause by far
- Never lazy-load the LCP element
- Preload the hero image and the headline font
- Reduce server response time — caching and better hosting
- Remove render-blocking CSS and JavaScript above the fold
Fixing INP
- Cut the amount of JavaScript running on the page
- Break long tasks into smaller pieces so the browser can respond between them
- Remove or defer third-party scripts — chat widgets and tag managers are common offenders
- Avoid heavy work in response to clicks and scrolls
Fixing CLS
- Set explicit width and height on every image and video
- Reserve space for ads, embeds and banners before they load
- Use font-display: swap and pick fallback fonts with similar metrics
- Never insert content above existing content after load — cookie bars are notorious for this
How to monitor over time
| Tool | Data type | Best for |
|---|---|---|
| Search Console — Core Web Vitals | Field | Site-wide trends and problem URL groups |
| PageSpeed Insights | Both | Diagnosing one page in detail |
| Chrome DevTools Lighthouse | Lab | Testing changes before deploying |
| Chrome UX Report | Field | Comparing against competitors |
Field data updates on a 28-day rolling window, so improvements take about a month to show fully. Do not panic when a fix does not appear in Search Console the next day.
Frequently asked questions
What are good Core Web Vitals scores?
LCP under 2.5 seconds, INP under 200 milliseconds, and CLS under 0.1. Google grades on the experience of 75% of your real visitors, not on an average.
How much do Core Web Vitals affect SEO?
They are a real but relatively small ranking factor — most useful as a tiebreaker between comparable pages. Their larger effect is on conversion, since slow pages lose visitors regardless of ranking.
Why does my Search Console data differ from PageSpeed Insights?
Search Console reports field data from real users over 28 days; the PageSpeed lab test simulates one visit on a throttled connection. Field data is what Google uses for ranking.