A page that opens a few seconds too late tests your visitors' patience — and directly affects your chances of a sale or an enquiry. Google uses three core metrics, known as Core Web Vitals, to measure the experience of real users. They are part of both the user experience and the signals considered in search rankings.
The three core metrics
- LCP (Largest Contentful Paint): the time it takes for the largest content element on the page, such as the main image or headline, to appear. 2.5 seconds or less is considered good.
- INP (Interaction to Next Paint): measures how quickly the page responds when a user clicks a button or opens a menu. 200 milliseconds or less is considered good. INP replaced the older FID metric in 2024.
- CLS (Cumulative Layout Shift): measures unexpected movement of elements while the page loads. 0.1 or less is considered good.
These values aren't judged on a single measurement but on the 75th percentile of real visitors' page loads. In other words, your site needs to be fast not just on your own powerful computer, but on the devices most of your visitors use.
How are they measured?
- PageSpeed Insights: shows real-user data (if there is enough traffic) and a lab test on one screen.
- Search Console: lists the Core Web Vitals report for all your pages and groups the problem pages.
- Browser developer tools: Lighthouse and the performance panel let you investigate the cause of a problem in detail.
The most common reasons websites are slow
- Unoptimised, oversized images
- Too many plug-ins and third-party scripts (chat tools, advertising pixels, social media widgets)
- Large JavaScript bundles that delay the main content
- Late-loading fonts and images without set dimensions that cause layout shifts
- Slow server response times and no caching
Where to start
- Serve images in modern formats (WebP, AVIF) at the right size, and lazy-load images below the fold.
- Give images and ad slots fixed dimensions to prevent layout shifts.
- Remove unused plug-ins and scripts, and defer the ones you need.
- Load the main hero image with priority and shorten server response times with caching.
- Use a CDN to deliver content from servers geographically close to your visitors.
How speed affects your business
Speed isn't just a technical score. Pages that load faster are abandoned less often, visitors view more pages, and form and checkout steps are completed more frequently. In ad campaigns, the landing page experience can also influence how the quality of your ads is assessed. That's why performance should be treated as a goal from the first day of design, not as a detail to add after launch.
Conclusion
In our projects we set a performance budget for every page, aim to keep LCP under 2.5 seconds and test every template on real devices before launch. If you'd like us to review your current website's performance, we can list the priority improvements in an audit report.
