An SEO aha moment: understanding Core Web Vitals
Last updated: July 26, 2024
What are Core Web Vitals?
Core Web Vitals are a set of specific factors Google considers important for a website's overall user experience. They're part of Google's Page Experience signals, used to assess web page quality.
These metrics focus on three aspects of user experience: loading, interactivity, and visual stability. Collectively, these are known as the three Core Web Vitals, which include the Largest Contentful Paint (LCP) for loading, First Input Delay (FID) for interactivity, and Cumulative Layout Shift (CLS) for visual stability.
Tip: Start by testing your site with Builder’s Performance Insights.
Why Core Web Vitals matter for SEO
Google uses Core Web Vitals as ranking factors. This means they directly impact your site's search engine performance.
Better Core Web Vitals scores can lead to the following:
- Higher search rankings
- Improved user experience
- Lower bounce rates
- Higher conversion rates
For site owners, understanding and optimizing Core Web Vitals metrics such as Largest Contentful Paint (LCP), First Input Delay (FID), and Cumulative Layout Shift (CLS) is crucial for improving user experience and site performance.
Core Web Vitals metrics
Let's break down each Core Web Vital:
1. Largest Contentful Paint (LCP)
LCP measures loading performance. It represents how quickly the main content of a page loads.
What's a good LCP score? Under 2.5 seconds.
To improve LCP:
- Implement effective image compression (consider using WebP or AVIF formats)
- Remove non-critical third-party scripts (like unused analytics or ad scripts)
- Upgrade server resources or implement a CDN
2. First Input Delay (FID)
FID measures interactivity. It quantifies when a user first interacts with your page and when the browser responds.
What's a good FID score? Less than 100 milliseconds.
To Improve FID:
- Minimize JavaScript execution time (use async/defer attributes)
- Implement code splitting to reduce the initial bundle size
- Use a web worker for heavy computations
3. Cumulative Layout Shift (CLS)
CLS measures visual stability. It represents how much unexpected layout shift occurs during the page's entire lifespan.
What's a good CLS score? Less than 0.1.
To Improve CLS:
- Set explicit width and height for media elements
- Avoid dynamically injecting content above existing elements
- Use CSS transform for animations instead of properties that trigger reflow
How to measure Core Web Vitals
You can measure Core Web Vitals using various tools, and there are several methods available for measuring core web vitals:
- PageSpeed Insights: URL-level analysis
- Google Search Console: Site-wide Core Web Vitals report
- Lighthouse: Comprehensive performance audits
- Chrome DevTools: Real-time performance monitoring
Additionally, the Chrome User Experience Report (CrUX) is a public dataset that provides insights into how real Chrome users interact with sites.
Strategies to improve Core Web Vitals
Improving your Core Web Vitals often involves technical optimizations:
Image optimization:
- Implement WebP or AVIF formats
- Use responsive images with srcset and sizes attributes
- Implement lazy loading with loading="lazy"
Code optimization:
- Minify and compress CSS/JS
- Implement tree shaking to eliminate dead code
- Use code splitting for large applications (e.g., React.lazy() and Suspense)
Caching:
- Implement browser caching with appropriate Cache-Control headers
- Utilize service workers