You’ve probably visited a website that looked fine… until it didn’t. The page took too long to load. Buttons lagged when you tapped them. The layout jumped just as you tried to read or click something. That experience is not just a UX problem. According to Google, it directly affects where your pages appear in search results. And that’s exactly what Core Web Vitals are designed to measure.
In today’s guide, we’ll break down what Core Web Vitals measure in plain language, what LCP, CLS, and INP mean for rankings, and how to improve them without overcomplicating things.
What Are Core Web Vitals? What Do They Measure?
Core web vitals answer one simple question: “How does this page feel to real users?” These metrics are based on real visitor data collected from Chrome users as they browse the web. They don’t rely only on simulations or ideal conditions. Instead, they reflect what actually happens when someone loads, taps, scrolls, or reads a page.
Core Web Vitals focus on three specific aspects of page experience:
- How fast the main content appears: Largest Contentful Paint (LCP)
- How quickly the page responds to interaction: Interaction to Next Paint (INP)
- How stable the layout stays while loading: Cumulative Layout Shift (CLS)
What they don’t measure is content quality or authority. A fast page with weak content will not suddenly rank well. Core Web Vitals come into play when pages are otherwise comparable. If two pages satisfy the same search intent equally well, the one that loads faster and responds more smoothly usually has the edge.
There’s another detail many sites overlook: Google evaluates Core Web Vitals at the 75th percentile. That means your site only passes if most users have a good experience. If performance is inconsistent, the metric fails.
Google’s Page Experience Ranking Factors Explained
Core Web Vitals sit within a broader system Google uses to evaluate how usable a page feels when someone lands on it. This system is known as the Page Experience Update. Think of it as a checklist. Content relevance still comes first. But once content quality is comparable, page experience helps decide which result feels better to visit.
Here is what Google currently looks at when assessing page experience:
- Core Web Vitals: User data that measures loading speed, responsiveness, and layout stability.
- HTTPS and security: Pages served securely are expected by default.
- Mobile friendliness: Layouts must adapt cleanly to different screen sizes.
- Intrusive interstitial control: Pop-ups and overlays that block content right after landing create friction
- Content layout clarity: Users should instantly recognize the main content. Ads and side elements shouldn't compete for attention.
Accessibility plays an important role here as well. Clear layouts and readable text contribute to how usable a page feels. We explore this in more detail in our blog: How to Design Your Website To Be Inclusive & Accessible for All Users
The Three Pillars of Core Web Vitals
1. Largest Contentful Paint (LCP): Loading Performance
Largest Contentful Paint (LCP) measures when the main content of a page becomes visible to the user. This is usually a hero image, a video, or a large block of text. For a good user experience, LCP should occur within 2.5 seconds of the page starting to load. LCP is basically what forms first impressions. If the main content loads late, users assume the site is broken.
Common Causes of Poor LCP
- Slow server response times: If the server takes too long to send the first byte of data (TTFB), the rest of the load delays inevitably.
- Resource load delay: The hero image or main text fights for bandwidth with less important scripts.
- Render-Blocking JavaScript and CSS: Browsers pause to read code files before they paint content. If these files are large, the screen stays blank.
How to Optimize LCP
- Improve server response time: distinct hosting improvements or using a Content Delivery Network (CDN) can lower Time to First Byte TTFB to under 800ms.
- Optimize large images: Use modern formats like WebP or AVIF. Compress aggressively without harming visual clarity.
- Reduce render-blocking resources: Defer non-critical CSS and JavaScript so the browser can paint important content sooner.
- Preload critical assets: Fonts, hero images, and key styles should be flagged for early loading.
- Use efficient caching rules: Static files shouldn't be reloaded on every visit. Proper cache headers help browsers reuse assets.
2. Interaction to Next Paint (INP): Responsiveness
INP tracks how quickly a page responds after a user interacts with it. This covers clicks, taps, and keyboard inputs. For a page to pass, interactions should respond within 200 milliseconds. A site with poor INP feels sluggish. You tap "Add to Cart," and the screen freezes. You click a menu, and nothing happens for half a second. These micro-delays build frustration.
Common Causes of Poor INP
- Heavy JavaScript execution: Large scripts running on the main thread block the browser from processing user clicks.
- Complex event handlers: If a click triggers a massive calculation, the browser can't update the screen until the calculation finishes.
- Excessive DOM nodes: A page structure with too many elements takes longer to update.
How to Optimize INP
- Reduce JavaScript execution: Remove unused libraries and scripts that lack a clear purpose.
- Break up long tasks: Any JavaScript task that runs for more than 50 milliseconds can block interactions. Splitting tasks into smaller chunks helps the browser stay responsive.
- Optimize event handlers: Ensure that interaction logic (what happens when you click) runs as fast as possible.
- Use background processing when needed: Complex calculations can be moved off the main thread so user interactions stay smooth.
3. Cumulative Layout Shift (CLS): Visual Stability
Cumulative Layout Shift (CLS) tracks how much visible content moves around while a page loads. For a good experience, the CLS score should stay at 0.1 or below.
Layout shifts are annoying. You’ve likely experienced reading an article when an ad suddenly loads, pushing the text down and making you lose your place. Or worse, you try to click "Cancel," but the button moves, and you hit "Confirm" instead.
Common Causes of Poor CLS
- Images without dimensions: If the browser doesn't know how big an image is before it loads, it can't reserve space for it.
- Ads and embeds: Dynamic content injected into the page often expands, pushing other elements aside.
- Web fonts: If a custom font loads slowly, the browser might swap it in after displaying a default font, causing the text to resize and shift.
How to Optimize CLS
- Set explicit dimensions: Always define width and height attributes for images and video elements.
- Reserve ad space: Use CSS to create a container with a fixed height for ad slots. If the ad doesn't load, the space remains empty rather than collapsing.
- Manage font loading: Use font-display: swap carefully or preload critical fonts to minimize text movement.
Layout stability is closely tied to how a site is designed and built. Decisions around templates, custom layouts, and component flexibility all influence CLS. We break down these trade-offs in our blog: Custom Web Design Vs Web Design Templates: Which Should You Choose for Your Brand?
Google Tools to Measure Your Performance
Understanding Core Web Vitals is only helpful if you can measure them accurately. The tools below give you a clear picture of how your pages perform for real users, not just in ideal test conditions.
- PageSpeed Insights: Google’s own tool reports LCP, INP, and CLS scores based on real user data and lab simulations. It highlights specific issues and suggests fixes. Remember: focus on actionable patterns, not just the score.
- Google Search Console: A must-have for monitoring site-wide performance trends. It flags pages that fail LCP, INP, or CLS thresholds and allows you to track improvements over time.
- Chrome User Experience Report (CrUX): This database collects anonymized metrics from Chrome users worldwide. It shows how visitors actually experience your site across devices, network conditions, and regions.
Explore our web design and development portfolio, where speed, stability, and usability are built into the work from the start.
Faster Pages, Better Rankings
Core Web Vitals may be technical in nature, but improving them is ultimately a business decision. A fast, responsive, and stable site requires collaboration between developers, designers, and marketers. Designers must account for image aspect ratios. Developers must write clean code. Marketers must optimize the assets they upload.
If you want a website that loads fast, responds smoothly, and stays visually stable across devices, our team at Road9 Media can help you get there.
Contact us today to start improving your site's performance in ways users notice and search engines respect.
