The three metrics in plain English
| Metric | What it measures | "Good" threshold | What a visitor notices when it's bad |
|---|---|---|---|
| LCP | Time until the largest visible element, often the hero image or heading, has loaded | ≤ 2.5 s | A blank or half-drawn page |
| INP | How quickly the page responds visually after a tap, click or key press | ≤ 200 ms | Buttons that seem to ignore taps |
| CLS | How much content jumps around while loading | ≤ 0.1 | Tapping the wrong thing because the layout moved |
The thresholds come from Google's Web Vitals documentation on web.dev (opens in a new tab), which recommends measuring at the 75th percentile of page loads, separately for mobile and desktop.
Why a business owner should care
Core Web Vitals are part of how Google evaluates page experience, but they are one signal among many. Relevant, helpful content still matters more for rankings. The stronger reason to care is your customers: a slow, jumpy page loses people before they read your offer, especially on mobile data.
Treat good vitals as a baseline of quality, not a ranking trick. A fast page that says nothing useful will not rank, and a useful page that is painfully slow will lose visitors.
How to check your own site for free
- PageSpeed Insights. Enter a URL at pagespeed.web.dev (opens in a new tab). If your site has enough traffic, the top section shows real-visitor data from the Chrome UX Report. The lower section is a lab test: useful for diagnosis, but it is a single simulated visit, not your customers' experience.
- Google Search Console. The Core Web Vitals report groups your URLs into Good, Needs improvement and Poor, using field data. You need to verify ownership of the site first.
- Your own phone. Open the site on a mid-range phone over mobile data. If it feels slow to you, it feels slow to customers.
The fixes that usually help most
For slow LCP
- Serve the hero image at the size it is displayed, in a modern format such as WebP or AVIF.
- Don't lazy-load the main above-the-fold image; lazy-load images further down instead.
- Reduce render-blocking CSS, fonts and scripts in the page head.
- Make sure the main content is in the HTML the server sends, not built later by JavaScript.
For poor INP
- Audit third-party scripts: chat widgets, trackers and pop-ups are frequent culprits.
- Remove unused apps or plugins; on Shopify, uninstalled apps can leave code behind in the theme.
- Break up long JavaScript tasks that run when users interact.
For high CLS
- Give images and video embeds explicit width and height, or a fixed aspect ratio.
- Reserve space for banners, cookie notices and ads instead of pushing content down.
- Load web fonts in a way that doesn't reflow text dramatically.
If your site is built with a JavaScript framework, read how client-side rendering affects SEO; the same change that helps search engines often improves LCP.
What to ask your developer or agency
- What are our field Core Web Vitals on mobile today, and which pages fail?
- Which single change would improve the worst metric most?
- Which third-party scripts do we load, and does each one still earn its place?
- How will we check the numbers after the change?
