Site Speed.

Site speed encompasses the suite of performance metrics measuring how quickly a website loads and becomes usable for visitors — including server response time (TTFB), total page load time, time to first byte, first contentful paint, and the Core Web Vitals metrics (LCP, INP, CLS). Site speed is both a Google ranking signal (since 2010 for desktop; 2018 for mobile) and a direct conversion rate driver.

Speed and Conversion Rates

Google's research consistently links page load time to conversion rate: a 1-second delay in mobile load time reduces conversion rates by up to 20%. Akamai found a 100ms delay reduces conversion rates by 7%. For e-commerce, where an additional 1% conversion improvement can mean millions in revenue, site speed optimisation competes with any paid channel for marketing ROI.

Key Speed Metrics

Time to First Byte (TTFB): how long after a request the first byte of the response is received — primarily a server and hosting performance indicator. First Contentful Paint (FCP): when the first text or image appears. Largest Contentful Paint (LCP): when the largest above-the-fold content element finishes loading. Total Blocking Time (TBT): how long the main thread is blocked by JavaScript. These metrics are measured in both lab conditions (PageSpeed Insights) and field data (CrUX).

Speed Optimisation Techniques

Core optimisations: serve images in modern formats (WebP, AVIF), implement lazy loading for below-the-fold images, minimise and defer JavaScript, use a content delivery network (CDN) for global delivery, enable browser caching, server-side rendering for JS-heavy frameworks, reduce third-party script load (analytics, chat, ad pixels), and upgrade to HTTP/2 or HTTP/3 for multiplexed request handling.