How it works
Core Web Vitals are three numbers. Each one measures a different part of how a page feels to use.
- Largest Contentful Paint (LCP) measures loading. It is the time until the largest piece of content on screen, often the main image or headline, appears. Good is 2.5 seconds or less.
- Interaction to Next Paint (INP) measures responsiveness. It is how long the page takes to visibly react after a click, a tap or a key press. Good is 200 milliseconds or less.
- Cumulative Layout Shift (CLS) measures visual stability. It is how much the content jumps around while the page loads. Good is 0.1 or less.
The numbers are measured on real visitors, not in a single lab test. That means the same page can score differently for people on fast and slow phones.
An example
You open a recipe page on your phone. The photo takes four seconds to appear. That is a slow LCP. You go to tap the print button, an ad loads above it and pushes the button down, and you tap the ad. That is a layout shift, and it raises CLS. You tap the menu and nothing happens for half a second. That is a slow INP.
Why it matters
- Visitors feel them. Slow, jumpy pages are frustrating to use.
- Google uses them. Google has said its ranking systems use Core Web Vitals. Relevant, useful content still matters more.
- They point to causes. A slow server, measured as time to first byte, holds back LCP. Images without set dimensions often cause layout shifts.
GOOD TO KNOWA new or low-traffic site may show no Core Web Vitals data at all. Real-visitor data needs enough visits before Google can report it.
How to check yours
- Open Google Search Console and go to the Core Web Vitals report. It groups your pages as good, needs improvement or poor.
- For a single page, use Google's PageSpeed Insights tool and read the real-user section at the top.
- Check the mobile results first, and make sure the page has a viewport tag so it fits small screens.
- Run the free audit for the server response time. It is not a full Core Web Vitals test.