Web performance: fixing Core Web Vitals
Speed isn't a nice-to-have — it directly affects how many visitors stay, convert, and how well you rank. Google's Core Web Vitals put numbers on the experience. Here's what they mean and how to fix them.
The three Core Web Vitals
- Largest Contentful Paint (LCP) — how quickly the main content appears. Aim for fast loading of the biggest visible element.
- Interaction to Next Paint (INP) — how quickly the page responds when users interact. Keep it snappy.
- Cumulative Layout Shift (CLS) — how much the page jumps around as it loads. Aim for stable, with no surprises.
The highest-impact fixes
- Optimise images. Right-sized, modern formats (like WebP), lazy-loaded below the fold — usually the biggest single win.
- Ship less up front. Load only what the first view needs; defer the rest.
- Reserve space for content. Set dimensions for images and embeds so the page doesn't jump (fixing CLS).
- Use caching and a CDN. Serve assets fast and close to the user.
- Measure on real conditions. Test on mid-range phones and real networks, not just a fast laptop.
Every second of delay costs you users — and search rankings.
- Core Web Vitals measure loading (LCP), responsiveness (INP) and stability (CLS).
- Image optimisation and shipping less up front are the biggest wins.
- Reserve space for content to stop layout jumps.
- Speed improves both conversion and SEO.
Frequently asked questions
Do Core Web Vitals affect SEO?
Yes — they're part of how Google assesses page experience. They're not the only ranking factor, but a fast, stable site helps both rankings and conversions.
What's usually the biggest performance problem?
Large, unoptimised images and loading too much JavaScript up front. Fixing those two often delivers the biggest improvement.
How do I measure my site's performance?
Free tools like Google PageSpeed Insights and Lighthouse report your Core Web Vitals and suggest specific fixes. Test on mobile, not just desktop.
ZIVARA builds fast sites and tunes existing ones to pass Core Web Vitals. Let's make yours faster. Related: UX mistakes that drive users away.