Website speed and performance for NZ businesses: Core Web Vitals and fixes that actually help

Speed is part UX, part credibility, part search quality. A slow mobile experience costs enquiries, especially for trades and tourism where users compare several tabs on patchy LTE.

1. Core Web Vitals in plain English

Google’s Core Web Vitals highlight three user-perceived issues:

• LCP (Largest Contentful Paint) — How quickly the main content becomes visible. Often dominated by hero images, sliders, or large blocks.
• INP (Interaction to Next Paint) — How snappy the page feels when people tap buttons, open menus, or submit forms—heavy JavaScript hurts here.
• CLS (Cumulative Layout Shift) — Whether things jump around while loading (ads, fonts, late images).

Use field data (real users) where available; lab tests help debugging but can mislead if your audience uses different devices.

2. Images: the usual LCP culprit

• Resize to display dimensions; avoid multi-megabyte uploads.
• Use modern formats (WebP/AVIF) with sensible fallbacks where needed.
• Reserve space (width/height attributes or aspect-ratio CSS) to reduce CLS.
• Lazy-load below-the-fold images—not your LCP candidate.

3. Fonts and layout shift

Web fonts can trigger FOIT/FOUT and shifts. Mitigate with font-display choices, subsetting, preloading critical fonts sparingly, and matching fallback metrics.

4. Caching layers

Understand what each layer does:

• Browser caching for static assets with versioned filenames.
• Page cache for anonymous HTML where safe.
• Object/database cache for expensive queries—especially WordPress.

Caches must exclude personalised routes (cart, account) or you will ship someone else’s basket.

5. Third-party scripts: the performance tax

Chat widgets, tag managers, heatmaps, and ad pixels each add main-thread work and network contention. Audit quarterly: remove what you do not read, defer non-critical loads, and test INP after each addition.

6. Hosting and TTFB

Slow time-to-first-byte points to server-side work: PHP, database, cold starts, or oversubscribed shared hosts. No amount of image compression fixes a multi-second TTFB.

7. WordPress-specific bloat

Audit plugins querying on every page load, autoloaded options, excessive cron jobs, and bloated revisions. Sometimes a leaner theme baseline saves more than another optimisation plugin.

8. After redesigns: regression testing

New hero videos, marketing banners, and tracking snippets often undo prior wins. Bake performance checks into launch sign-off.

9. Frequently asked questions