Session overview
A 38-minute crash course on Core Web Vitals — what they measure, why they matter, and the specific optimisations that produce measurable improvements.
The three metrics
- LCP (Largest Contentful Paint). What it measures, how to improve it, why 80% of LCP problems are images.
- INP (Interaction to Next Paint). The successor to FID. Why too much JavaScript is the usual culprit.
- CLS (Cumulative Layout Shift). What causes layout shift and how to prevent it.
What actually moves the needle
The session walks through specific optimisations in order of impact:
- Image strategy: AVIF, WebP, srcset, preloading, fetchpriority.
- JavaScript audit: bundle analysis, code splitting, third-party script deferral.
- Font strategy: self-hosting, size-adjust, preload.
- Layout stability: explicit dimensions, reserved space for embeds.
What doesn't matter as much as you think
The session also covers commonly-overrated optimisations:
- HTTP/3 vs HTTP/2 in 2026.
- Service Worker complexity for sites that don't need offline.
- Server response time tuning when it's already adequate.
- Critical CSS inlining for sites with small CSS bundles.
Live demonstration
Includes a live audit of a slow production site, identifying the top three changes that would deliver the biggest performance gains.
Reference materials
The optimisations covered are documented in our Core Web Vitals blog post and Astro performance guide. Business framing in our economics of web performance whitepaper.
Recording
Contact us to request the recording.