Core Web Vitals: Reading LCP, INP and CLS from a Hosting Perspective

Core Web Vitals are the three metrics Google uses to measure real user experience. Understanding them lets you tell whether a "slow site" complaint comes from the server or from the page itself.

The three metrics and their good values

INP replaced FID in March 2024. If an older guide talks about FID, that information is out of date. Assessment is based on the experience of 75% of visitors.

Where to see the values

• PageSpeed Insights: enter your address; if there's enough visitor data it shows real-user results, otherwise only a lab test.
• Google Search Console: the "Core Web Vitals" report lists problem pages in groups.
• Browser developer tools: the Performance tab shows which file or piece of code causes the problem.

LCP: the metric hosting affects most

The first part of LCP is the time for the server to send its first response (TTFB). Page caching shortens it more than anything else. On LiteSpeed servers the most direct way is the LiteSpeed Cache plugin.

The rest depends on the page:

• Shrink the main image, use WebP or AVIF and don't lazy-load it. See the image optimisation guide.
• Reduce large CSS and JavaScript files that block the top of the page.
• If your visitors are far away, consider whether a CDN helps. See server location or CDN?

INP: mostly a JavaScript problem

Poor INP is usually caused by heavy JavaScript running in the browser: many tracking scripts, chat bubbles, sliders and page builders' extra scripts. Upgrading the server rarely improves INP. Removing unused plugins and third-party code is the most effective step.

CLS: shifting content

• Give images and video embeds a width and height.
• Reserve space in advance for ads, banners and cookie notices that load later.
• If late-loading web fonts make text jump, review the font-display setting.

When is hosting really the problem?

If server response time is high even for cached pages, or the site slows noticeably at busy times, your account may be hitting its resource limits. Check the resource usage statistics in cPanel and read them with our CPU, RAM and I/O limits article.