Why Are Core Web Vitals Important? CWV are considered to be essential indicators of the overall quality of a website and are used by Google to evaluate the performance of web pages and to determine their ranking in search results. Google announced three metrics for web performance that have come to be called Core Web Vitals (CWV). The announcement was still part of the search engine giant’s goal to provide the best web experience for users. These metrics are: First Input Delay (FID), Cumulative Layout Shift (CLS), and Largest Contentful Paint (LCP).