Load is not a single moment in time — it’s an experience that no one metric can fully capture. Shubhie Panicker, Google EngineerAnyone familiar with optimizing their Lighthouse score will appreciate the multi-stage journey that begins whenever a new page is clicked. But, if there is one moment in the loading of a page that seems to demand more attention than others it’s the First CPU Idle. First CPU idle is the time it takes for a page’s main thread to be quiet enough to handle input from the user. Despite the nuances of what defines loading, this is the line most users would define as the point between ‘loading’ and ‘loaded’. That’s why it’s so crucial. As one of the 6 measurements in the Performance section of Google’s Lighthouse score (accounting for 13% of total weighting), cutting the first CPU idle time is key to improving Lighthouse scores, SEO results, and user experiences.