Google measures how real visitors experience your pages with three metrics called Core Web Vitals. They are also part of how Google evaluates page experience.
The three metrics
| Metric | What it measures | "Good" threshold (Google) |
|---|---|---|
| LCP (Largest Contentful Paint) | How long until the main content appears | 2.5 seconds or less |
| INP (Interaction to Next Paint) | How quickly the page responds to taps and clicks | 200 milliseconds or less |
| CLS (Cumulative Layout Shift) | How much the page jumps around while loading | 0.1 or less |
Source: Google's web.dev documentation on Core Web Vitals.
Most common causes of a slow site
- 1Large, unoptimized images. A photo straight from a camera can be many times bigger than needed.
- 2Too much JavaScript. Chat widgets, trackers and sliders all add code the phone has to process.
- 3Web fonts loaded the slow way. Too many font files delay the text.
- 4Slow hosting or no caching.
- 5Content that appears late, such as banners pushed in after the page loads (this hurts CLS).
How to check your own site
- PageSpeed Insights (pagespeed.web.dev) shows both lab results and, if your site has enough traffic, real visitor data.
- Search Console has a Core Web Vitals report for your whole site.
Want us to look at your site's speed? Get in touch.