Short answerGoogle measures three Core Web Vitals: Largest Contentful Paint should happen within 2.5 seconds, Interaction to Next Paint should be 200 milliseconds or less, and Cumulative Layout Shift should be 0.1 or less. They are judged at the 75th percentile of real visits, for mobile and desktop separately. Because Google indexes the mobile version of a page, the phone result is the one that counts most.
A guest standing outside a restaurant in Dubai Mall, on a phone connection that is busy because everyone else is also on it, taps your link. The page shows a blank screen for four seconds. By the time the menu appears, they have chosen the place next door.
The three numbers
Google calls them the Core Web Vitals and publishes the targets for a good experience.
- Largest Contentful Paint, LCP. How fast the main content appears. Good is within 2.5 seconds of when the page starts loading.
- Interaction to Next Paint, INP. How quickly the page reacts when someone taps or types. Good is 200 milliseconds or less.
- Cumulative Layout Shift, CLS. How much the page jumps around while it loads. Good is 0.1 or less.
Google evaluates these at the 75th percentile of page loads, separately for mobile and desktop. That means three out of four visits should meet the target, not just the average one.
Why the phone result matters most
Google uses the mobile version of your pages for indexing and ranking. If your phone site is slower or has less content than your desktop site, the phone version is the one that is judged. Test on a phone first.
What usually slows a page down
Google's guidance on Largest Contentful Paint names four parts. Fix them together, because speeding up one part often moves the delay to another.
- A slow first response. Redirects, a distant server and pages that cannot be cached delay the first byte. Minimise redirects, use a content delivery network and speed up the server.
- The main image or font is found late. Do not load it with script, and never lazy-load the main image. Make it discoverable in the page's HTML and preload it when needed.
- Files that are too big. Serve correctly sized images in modern formats such as WebP or AVIF, compress them and reduce font files.
- Blocking code. Large stylesheets and scripts in the page head hold up painting. Inline or defer what is not critical and break up long scripts.
On many small business sites the culprit is a single huge photo or a video that starts loading before the page does. A header picture of several megabytes can easily miss the 2.5 seconds on a busy phone connection.
Videos and sliders
A short background video can look good. Keep the file small, give it a poster image so something appears at once, and let it load only when it is on screen. A slider that loads ten large photos before you see the first one costs you visitors for no gain.
How to test your site
- Open Google's PageSpeed Insights, enter your address and read the mobile result first.
- In Search Console, look at the Core Web Vitals report, which shows how real visitors experienced your pages.
- Try the site yourself on a phone with the Wi-Fi switched off, at a time of day when the network is busy.
- Test the pages that matter: the home page, the menu or price page and the contact page.
This week
- Run your home page through PageSpeed Insights and write down the LCP, INP and CLS.
- Find the largest image on the home page and check its file size.
- Check that the phone version shows the same content as the desktop version.
- Ask whoever hosts your site where the server is, and whether a content delivery network is in use.
Speed is one part of SEO and of a good first impression. See the full list in an SEO checklist for a small business in Dubai.
Questions
What is a good loading time for a website?
Google's target for Largest Contentful Paint is within 2.5 seconds of when the page starts loading, measured for at least 75 percent of visits.
What are the Core Web Vitals?
Three measurements: Largest Contentful Paint for loading, Interaction to Next Paint for responsiveness and Cumulative Layout Shift for visual stability. Good scores are 2.5 seconds, 200 milliseconds and 0.1.
Does website speed affect Google rankings?
Google publishes the Core Web Vitals as the targets for a good page experience, and it indexes the mobile version of your pages, so a slow or incomplete phone site is the one that is judged. Nobody outside Google can say how much speed counts against other factors.
How do I check my website speed?
Use PageSpeed Insights for a test of one page and the Core Web Vitals report in Search Console for real visitor data.
Why is my website slow on mobile?
The usual causes are a slow first response from the server, a large main image, big font or script files and code that blocks the page from painting.