Core Web Vitals are a set of specific factors that Google considers crucial for the overall user experience on a webpage. They are part of Google’s page experience signals, which also include mobile-friendliness, safe-browsing, HTTPS security, and no intrusive interstitials. Core Web Vitals specifically focus on three main aspects of web page performance: loading, interactivity, and visual stability.
The Three Core Web Vitals
- Largest Contentful Paint (LCP):
- Definition: Measures loading performance. Specifically, it marks the point in the page load timeline when the main content of the page has likely loaded.
- Good Threshold: LCP should occur within 2.5 seconds of when the page first starts loading.
- First Input Delay (FID):
- Definition: Measures interactivity. It quantifies the experience users feel when trying to interact with unresponsive pages. It tracks the delay between the first user interaction with a page (like clicking a link) and the time when the browser begins processing that interaction.
- Good Threshold: Pages should have an FID of less than 100 milliseconds.
- Cumulative Layout Shift (CLS):
- Definition: Measures visual stability. It calculates the sum total of all individual layout shift scores for every unexpected layout shift that occurs during the entire lifespan of the page.
- Good Threshold: Pages should maintain a CLS of less than 0.1.
Impact on SEO
- Ranking Factor:
- Core Web Vitals are used by Google as ranking signals. Websites that perform well on these metrics are likely to rank higher in search results, while those with poor performance may see a decline in rankings.
- User Experience:
- Improving Core Web Vitals can enhance the user experience, leading to lower bounce rates and higher engagement. A fast and responsive website encourages users to stay longer and interact more, which can indirectly boost SEO through improved behavioral metrics.
- Mobile-First Indexing:
- Given Google’s mobile-first indexing approach, Core Web Vitals are especially important for mobile users. Optimizing these metrics ensures a better mobile experience, which is critical as the majority of web traffic now comes from mobile devices.
Optimizing Core Web Vitals
- Largest Contentful Paint (LCP):
- Optimize server response times (e.g., using faster hosting services).
- Use a Content Delivery Network (CDN).
- Improve resource load times (e.g., compress images and text files).
- Prioritize above-the-fold content loading.
- First Input Delay (FID):
- Minimize JavaScript execution.
- Break up long tasks.
- Use a web worker to run JavaScript in the background.
- Optimize the main-thread work.
- Cumulative Layout Shift (CLS):
- Use set size attribute dimensions for any media (images, videos, etc.).
- Ensure ads, embeds, and iframes have reserved space.
- Add new UI elements below the fold, so they don’t push content down unexpectedly.
Monitoring and Tools
- Google Search Console: Provides reports specifically for Core Web Vitals.
- PageSpeed Insights: Offers detailed analysis and suggestions for improving LCP, FID, and CLS.
- Lighthouse: A developer tool integrated into Chrome DevTools for auditing page performance.
- Web Vitals Extension: A Chrome extension that measures Core Web Vitals in real-time as users navigate your site.
This alignment of technical SEO and user experience ultimately drives more organic traffic and engagement.