Page Speed and SEO: What Actually Moves Rankings

Google has confirmed page experience signals — including page speed — affect rankings. The effect is modest on its own, but compounds with bounce rate, dwell time, and conversion data into a meaningful difference at scale.

Image weight is 80% of the problem

Across most sites, images are 60-80% of page weight. Compress to AVIF or WebP, serve responsive srcset, lazy-load below-the-fold, and use a CDN. This single change typically halves LCP.

Third-party scripts are the second biggest

Audit your tag manager, chat widgets, A/B testing tools, and analytics. Each one blocks the main thread. Defer non-critical scripts and use partytown for chat/analytics where possible.

Cache aggressively at the edge

Pages that don't need personalization should be cached at the CDN for hours or days. Cloudflare, Fastly, Vercel Edge — they're cheap and they fix Time To First Byte (TTFB) for free.

Don't chase 100 Lighthouse scores

Lighthouse is a lab tool. Field data (CrUX) is what Google ranks on. A 75 Lighthouse score with great real-user metrics outranks a 100 score with bad field data every time.

Free tools to apply this

FAQ

What page speed tool should I use?

PageSpeed Insights for a quick check (it shows both lab and field data), and web.dev/measure for diagnostics with specific code-level recommendations.

Is mobile or desktop speed more important?

Mobile. Google uses mobile-first indexing — your mobile experience is the one being ranked.

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