PageSpeed / Load Time

PageSpeed describes how quickly a website loads and responds to user input. PageSpeed optimisation bundles all measures that improve loading time, responsivenessInteraction to Next Paint (INP) measures how quickly a page responds to user input across all interactions and represents interactivity.Open glossary entry → and visual stabilityCumulative Layout Shift (CLS) measures how much visible elements shift unexpectedly during loading and represents the visual stability of a page.Open glossary entry →, and is reflected in the Core Web VitalsCore Web Vitals are a set of Google metrics that measure real-world user experience in the areas of loading performance, interactivity and visual stability.Open glossary entry → (LCPLargest Contentful Paint (LCP) measures when the largest visible content element in the viewport has loaded, representing the perceived loading speed.Open glossary entry →, INP, CLS).

The right framing matters: PageSpeed optimisation does not mean chasing a perfect Lighthouse scoreLighthouse is an open-source diagnostic tool from Google that audits a page's performance, accessibility and other quality aspects in a simulated lab environment.Open glossary entry →. The goal is a fast, stable and user-friendly page based on real user dataField data are performance measurements based on real users and their actual devices and connections. They show whether a performance problem is genuinely relevant.Open glossary entry →. A fast page with poor content does not automatically gain visibility, while a slow page with good content wastes user experience and conversion potential.

The biggest levers are:

• optimising images (compression, WebPWebP and AVIF are modern, space-saving image formats that produce much smaller files than JPEG or PNG at comparable quality, improving loading time.Open glossary entry →/AVIF, responsive delivery),
• improving server response and cachingCaching stores previously retrieved content so it is available faster on repeat requests, relieving both servers and the network.Open glossary entry →,
• reducing render-blocking CSSRender-blocking resources are files such as CSS or JavaScript that the browser must load and process before it can render the page, thereby delaying rendering.Open glossary entry → and unnecessary JavaScript,
• controlling fonts and third-party scripts.

Prioritisation focuses on pages where many real users, important rankings or conversion goals are affected.