Core Web Vitals

What Are Core Web Vitals?

Core Web Vitals are three metrics defined by Google that evaluate how well users experience a website. They specifically measure a page's loading time, responsiveness, and visual stability. Since 2021, they have been an official ranking factor: websites that perform well here have a measurable advantage in Google search results.

For website operators, Core Web Vitals are therefore doubly relevant. They improve the user experience and simultaneously support visibility in search results.

The Three Core Web Vitals in Detail

1. Largest Contentful Paint (LCP) – Loading Time

LCP measures how long it takes for the largest visible element on a page to load. This could be a main image, a video thumbnail, or a large text block. Simply put: How quickly does the visitor see the main content?

• Good: under 2.5 seconds
• Needs improvement: 2.5 to 4 seconds
• Poor: over 4 seconds

2. Interaction to Next Paint (INP) – Responsiveness

INP replaced the former First Input Delay (FID) as an official Core Web Vital in March 2024. While FID only measured the first interaction, INP evaluates the overall interaction performance of a page throughout the entire visit. Specifically, it measures the delay between user actions (clicks, keyboard inputs, touch inputs) and the visible response of the page.

• Good: under 200 milliseconds
• Needs improvement: 200 to 500 milliseconds
• Poor: over 500 milliseconds

3. Cumulative Layout Shift (CLS) – Visual Stability

CLS measures how much the content of a page shifts during loading. Who hasn’t experienced this: You want to click a button, and at the same moment, an ad banner loads, causing the button to jump down. Such layout shifts frustrate users and lead to misclicks.

• Good: under 0.1
• Needs improvement: 0.1 to 0.25
• Poor: over 0.25

How Can Core Web Vitals Be Improved?

Optimise LCP (faster loading time):

• Compress images and deliver them in modern formats like WebP or AVIF
• Enable browser caching so returning visitors don’t have to reload files
• Choose fast hosting, ideally with a Content Delivery Network (CDN)
• Remove unnecessary plugins and scripts

Optimise INP (better responsiveness):

• Keep JavaScript lean and remove unused code
• Split long script tasks into smaller sections
• Reduce third-party scripts like tracking and advertising tools to the essentials

Optimise CLS (more stable layout):

• Specify fixed height and width attributes for images and videos in HTML
• Provide fixed placeholders for ads and embedded content
• Integrate fonts in a way that prevents text jumps during loading (e.g., with font-display: optional)
• Avoid inserting new content above already visible content

Tools for Measurement

Core Web Vitals can be checked using various free tools:

• Google PageSpeed Insights: Provides values for a single URL, including specific optimisation suggestions.
• Google Search Console: Shows an overview of all URLs on a website in the "Core Web Vitals" report, grouped by rating.
• Lighthouse: Integrated directly into Chrome DevTools, suitable for detailed analyses during development.
• web.dev/measure: Offers a comprehensive analysis with actionable recommendations.

Conclusion

Core Web Vitals make measurable what users already feel: whether a website is fast, responsive, and stable. Those who regularly measure and optimise in a targeted way improve both the user experience and their position in search results. The effort is particularly worthwhile because fast pages lead to longer dwell times and higher conversion rates, which directly impacts business results.