Page Speed

Page speed is a broad description of how quickly a page responds and presents useful, stable content to a visitor. No single measurement captures it. Loading indicators such as Time to First Byte (TTFB), First Contentful Paint (FCP), and Largest Contentful Paint (LCP) describe different stages, while Interaction to Next Paint (INP) measures responsiveness and Cumulative Layout Shift (CLS) measures visual stability. A synthetic test models one environment; field data records eligible real-user experiences.

Why it matters: Start with the journeys and audiences that matter, then segment field data by page type, device, geography, and connection where the sample supports it. Use lab traces to reproduce a slow experience and separate server response, render-blocking work, resource discovery, download time, main-thread tasks, and layout shifts. Priorities vary by page: improve delivery and caching, compress and size media, remove unnecessary code, load critical resources deliberately, reduce third-party cost, and protect interaction responsiveness. Measure before and after in the same conditions and watch errors and business outcomes. Google uses Core Web Vitals in its ranking systems, but speed metrics do not directly determine a position. There is no universal conversion loss per second; impact depends on the audience, task, page, device, baseline, and change.