First Input Delay (FID) measures the time it takes for a webpage to respond to the first user interaction, such as a click or scroll. FID is one of Google’s Core Web Vitals, impacting user experience and search rankings.

Improving FID creates a smoother, more responsive user experience, which benefits ad visibility and engagement. For advertisers, a low FID score means users are less likely to abandon the page, increasing the chances of ad interaction and engagement.