FFirst Input Delay (FID)

First Input Delay (FID) measures the time gap between when a user first interacts with your website—whether that's clicking a button, tapping a link, or typing into a form—and when the browser actually responds to that action. It's one of Google's Core Web Vitals, alongside Largest Contentful Paint and Cumulative Layout Shift, and directly influences both user experience and search engine rankings.

For business owners, FID matters because it reflects how snappy your site feels. A slow response to user input frustrates visitors and often leads to abandonment. If someone clicks a checkout button and nothing happens for 300 milliseconds, they might assume the click didn't register and click again—or leave entirely. Poor FID damages conversion rates, increases bounce rates, and signals to Google that your site isn't performing well for users.

FID occurs because browsers run JavaScript on the main thread. When your page loads heavy scripts or executes resource-intensive tasks, the browser can't respond immediately to user input—it's busy processing JavaScript. This is why FID is closely linked to how much JavaScript your site uses and how well that code is optimised. Modern frameworks, unoptimised third-party scripts, and poor code splitting all contribute to high FID.

At Dino Media, we optimise FID by auditing your JavaScript performance, implementing code splitting and lazy loading, deferring non-critical scripts, and using performance monitoring tools like Lighthouse and Google's Page Speed Insights. We ensure your hosting and server configuration support fast response times, and we design sites with performance as a core principle from the start.