Website Accessibility and WCAG: A Guide for Product Teams
What WCAG means for your website or app, which accessibility issues matter most, and how to build and test accessibility into outsourced development.
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Core Web Vitals explained: making your web app fast for users and Google
What LCP, INP and CLS measure, the thresholds you should aim for, and the engineering changes that improve them in modern web applications.
Speed is a feature. Fast sites convert better, rank better and feel more trustworthy. Google’s Core Web Vitals give you three measurable signals of real-world user experience — and a clear target for your engineering team.
The three metrics
| Metric | What it measures | “Good” threshold |
|---|---|---|
| LCP — Largest Contentful Paint | How quickly the main content appears | 2.5 seconds or less |
| INP — Interaction to Next Paint | How quickly the page responds to clicks, taps and typing | 200 milliseconds or less |
| CLS — Cumulative Layout Shift | How much the layout jumps around while loading | 0.1 or less |
Google assesses these at the 75th percentile of real visits, so improvements must work for users on mid-range phones and slower networks — not just your laptop.
Improving LCP
- Serve optimised images in modern formats at the right size, and preload the hero image.
- Render critical content on the server or at build time instead of waiting for JavaScript.
- Use a CDN and keep server response times low.
- Inline critical CSS and defer non-critical styles and scripts.
Improving INP
- Ship less JavaScript. Remove unused libraries and split bundles by route.
- Break up long tasks so the main thread stays responsive.
- Defer third-party scripts such as chat widgets and trackers.
- Avoid heavy work in input handlers; update UI first, compute later.
Improving CLS
- Always set width and height (or aspect ratio) on images, videos and embeds.
- Reserve space for ads, banners and dynamic content.
- Load web fonts with sensible fallbacks to avoid text reflow.
Measure continuously
Use field data from real users (for example, Chrome’s user experience data in Search Console) alongside lab tools such as Lighthouse. Add performance budgets to CI so regressions are caught before they ship.
Build fast from the start
Architecture choices — static generation, server rendering, edge caching and lean front ends — matter more than late optimisation. This very website is a statically generated Astro site that loads its 3D scenes only when they scroll into view.
Our web application development team builds with performance budgets from day one. Get in touch for a performance review of your site or app.