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SEO Glossary

Site Speed

Definition

Site speed is the complete time journey from when a user clicks a link to when they can fully interact with a webpage, covering server response, visual loading, and full interactivity.

Also known as: Page speedWebsite performanceLoad time

Explained

Site speed encompasses the total time from when a user clicks a brand’s link to when they can fully interact with the webpage content. It includes multiple performance layers: server response time (Time to First Byte), visual loading completion, and full interactivity achievement. Modern optimisation focuses on perceived performance — how quickly users feel a site responds to their needs.

Why Site Speed Matters

Fast-loading sites improve user experience, search rankings, conversion rates, and brand perception. Google’s Core Web Vitals significantly influence rankings, and brands with load times under 2.5 seconds see higher conversion rates and customer lifetime value. Mobile-first indexing also makes speed essential, as mobile users abandon slow sites far more quickly than desktop users.

Key Optimisation Factors

  • Server response time (TTFB) under 200ms
  • Image optimisation using next-generation formats such as WebP and AVIF
  • Efficient JavaScript and CSS delivery, including async loading and critical CSS
  • Content Delivery Network (CDN) deployment for global performance
  • Mobile-first performance strategies, including PWAs and AMP where appropriate
  • Browser caching and service workers to speed up repeat visits

Example

An e-commerce brand that reduces page load time from 4+ seconds to under 2 seconds can increase conversion rates by an average of 74% and reduce abandoned cart rates by 35%.