What you will learn
- Explain what LCP, INP and CLS measure
- Improve performance with optimised images, fonts and less JavaScript
- Add a sitemap and robots.txt and submit a site to Google Search Console
Google's Core Web Vitals measure real user experience. Largest Contentful Paint (LCP) measures how quickly the main content appears, with 2.5 seconds or less considered good. Interaction to Next Paint (INP) measures how quickly the page responds to clicks and taps, with 200 milliseconds or less considered good. Cumulative Layout Shift (CLS) measures unexpected movement, with 0.1 or less considered good.
Most improvements come from a few habits. Serve images at the size they are displayed, in modern formats, with width and height set. Load the main hero image early and lazy-load images further down. Limit custom fonts. Ship less JavaScript by keeping client components small. Lighthouse in Chrome developer tools gives a quick lab report, while PageSpeed Insights also shows field data from real visitors when it exists.
Technical SEO makes sure search engines can find and understand your pages. An XML sitemap lists the URLs you want indexed, and a robots.txt file tells crawlers what not to fetch. Next.js can generate both from sitemap.ts and robots.ts files in the app directory. Verify your site in Google Search Console, submit the sitemap and check the indexing reports for problems.