Site Speed.
Learn what Site Speed means in modern search and SEO.
The measure of how quickly a website loads for users, encompassing server response time, resource loading, and rendering performance, a direct ranking and conversion factor.
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.
Articles about Site Speed
Read more on the Aergos blog.
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