Page speed has been a Google ranking factor since 2010. But it wasn’t until the rollout of Core Web Vitals as an official ranking signal in 2021 and their gradual tightening through 2026 that Google made its standards explicit, measurable, and publicly auditable.
What Are Core Web Vitals?
1. Largest Contentful Paint (LCP)
LCP measures how long it takes for the largest visible element on the page to load Google’s proxy for ‘how quickly does the page feel like it’s loaded?’
- Good: LCP under 2.5 seconds
- Needs improvement: LCP between 2.5 and 4 seconds
- Poor: LCP over 4 seconds
2. Cumulative Layout Shift (CLS)
CLS measures visual instability how much page elements unexpectedly move while loading. If you’ve ever been reading a page, a banner loads above you, and the text jumps down that’s high CLS.
- Good: CLS score under 0.1
- Needs improvement: CLS between 0.1 and 0.25
- Poor: CLS over 0.25
3. Interaction to Next Paint (INP)
INP replaced First Input Delay in March 2024. It measures how quickly the page responds when someone clicks a button, taps a link, or types in a field.
- Good: INP under 200 milliseconds
- Needs improvement: INP between 200 and 500 milliseconds
- Poor: INP over 500 milliseconds
Why Core Web Vitals Matter for SEO
Google uses Core Web Vitals as a ranking signal within its ‘Page Experience’ system. When two pages are closely matched in content quality and authority, the one with better Core Web Vitals scores ranks higher. More practically: pages with good scores have significantly lower bounce rates and higher conversion rates. Users leave slow, unstable pages.
How to Check Your Core Web Vitals
- Google PageSpeed Insights: Go to pagespeed.web.dev and enter your URL. Provides both lab data and real-world field data from Chrome users.
- Google Search Console: The Core Web Vitals report shows real-world data for your entire site, grouped by Good, Needs Improvement, and Poor URLs.
- Chrome DevTools: For developers, provides detailed waterfall analysis showing which resources load, in what order, and how long each takes.
Fixing LCP (Slow Loading Main Content)
- Compress and resize images: Use WebP or AVIF formats, compress before uploading, specify dimensions. The single most impactful action for most websites.
- Use fast hosting: Budget shared hosting is a common cause of poor LCP. A good CDN and fast server response time are essential.
- Preload the LCP element: Adding a preload hint for your hero image tells the browser to prioritise loading it.
- Reduce server response time: Fast hosting, server-side caching, and reducing database queries all help TTFB.
Fixing CLS (Unexpected Layout Shifts)
- Set width and height on all images: When images have explicit dimensions, the browser reserves space before loading, preventing layout shift.
- Reserve space for ads: Ensure ad slots have fixed dimensions so layout doesn’t shift when ads load.
- Avoid injecting content above existing content: Banners and cookie notices that load above existing elements cause CLS.
Fixing INP (Slow Interaction Response)
- Reduce JavaScript execution time: Heavy frameworks and plugins that execute during page load block user interactions.
- Break up long tasks: Code running for more than 50 milliseconds blocks the main thread. Split tasks to allow interactions to be handled more promptly.
| ⚡ Find Out What Your Core Web Vitals Scores Mean Book a free SEO audit at lobodigital.co.uk |
