Google PageSpeed Insights is an excellent starting point for speed optimisation. But most sites reach a score of 70–85 implementing its recommendations and then plateau — the remaining 15–30 points require techniques that PageSpeed does not surface. This guide covers the advanced optimisation approaches that move the needle when you have already addressed the standard recommendations.

Font Optimisation Beyond the Basics

PageSpeed recommends eliminating render-blocking resources, which includes Google Fonts loaded with a standard <link> tag. But most sites implement this partially — they add display=swap to eliminate render blocking but still experience Cumulative Layout Shift (CLS) from font swapping and Largest Contentful Paint (LCP) delays from the font download.

The complete font optimisation stack in 2026:

1. Self-host your fonts. Loading fonts from Google Fonts requires a DNS lookup, TCP connection, and TLS handshake to fonts.googleapis.com before the font file even starts downloading. Self-hosting eliminates this entire round-trip. Download your fonts using google-webfonts-helper.herokuapp.com and serve them from your own domain.

2. Preload critical fonts. Add <link rel="preload" href="/fonts/your-font.woff2" as="font" type="font/woff2" crossorigin> for fonts used in your above-the-fold content. Preloading starts the font download immediately, eliminating the FOUT (Flash of Unstyled Text) that causes CLS.

3. Use font-display: optional for non-critical fonts. Unlike display=swap which shows fallback text then swaps (causing CLS), display: optional only uses the custom font if it loads within a very short window — preventing the swap entirely for users on slow connections.

Third-Party Script Optimisation

Third-party scripts — analytics, chat widgets, advertising scripts, social widgets — are consistently the largest source of unexplained performance problems that PageSpeed does not fully account for. Each third-party script adds: a DNS lookup, a TCP connection, potentially a TLS handshake, and JavaScript execution time that competes with your own scripts for the main thread.

As we covered in our guide to mobile Core Web Vitals, JavaScript execution time is the primary driver of poor INP scores. Third-party scripts executing on the main thread block all user interactions while they run.

Partytown — an open-source library that moves third-party scripts off the main thread into a web worker. Supported by most analytics and tag managers including Google Analytics 4. Implementing Partytown can improve INP scores by 50–150ms for sites with heavy third-party scripts.

Lazy loading third-party scripts. Defer loading chat widgets, social share buttons, and recommendation engines until after the user's first interaction. A visitor who bounces within five seconds never needed the chat widget to load at all — loading it anyway wasted 200–400ms of their initial page load.

Edge Caching and CDN Configuration

A CDN serves your content from servers physically close to your users, reducing network latency. Most basic CDN configurations cache static files (images, CSS, JavaScript) but leave HTML uncached — resulting in every page request still hitting your origin server. Edge caching HTML changes this.

Cloudflare's cache rules (on their free plan) can cache HTML pages at the edge with appropriate cache invalidation on content updates. For sites where page content does not change per user (most blogs, marketing sites), HTML edge caching reduces TTFB from 200–800ms to 10–50ms — a dramatic improvement that reduces LCP without any content changes.

Resource Hints: Preconnect, Prefetch, Preload

Resource hints tell the browser about resources it will need before it encounters them in the HTML:

preconnect — establishes a connection to a domain before you request resources from it. Use for: your CDN, your font provider (if not self-hosting), and any third-party domains your page requests from.

preload — downloads a specific resource immediately, before the parser encounters it. Use for: your LCP image, critical fonts, and above-the-fold CSS that is loaded from a separate file.

prefetch — downloads resources that will likely be needed on the next page visit. Use for: the next article in a series, the checkout page from a product page. Improves perceived performance for multi-page user journeys.

Image Optimisation Beyond WebP

AVIF format provides 30–50% smaller files than WebP at equivalent quality for most images. Browser support for AVIF reached 95%+ in 2024. Serve AVIF to supporting browsers using the picture element:

<picture>
  <source srcset="image.avif" type="image/avif">
  <source srcset="image.webp" type="image/webp">
  <img src="image.jpg" alt="Description">
</picture>

Combined with our page speed tool to identify your largest image payloads, switching to AVIF can reduce total page weight by 25–40% for image-heavy pages.

Summary

Advanced speed optimisation beyond PageSpeed basics includes self-hosting fonts with preloading, Partytown for third-party script off-main-thread execution, HTML edge caching on CDNs, strategic resource hints (preconnect/preload/prefetch), and AVIF image format. Combined with the standard optimisations identified by our speed checker, these advanced techniques achieve the top-tier Core Web Vitals scores that provide a measurable ranking advantage in competitive niches.

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