Learn about the differences between FID and INP and how to optimize your website's INP score. As of March 2024, Interaction to Next Paint (INP) will replace the First Input Delay (FID) as a new Core Web Vital. First Input Delay is a web performance metric that measures the time between a user's very first interaction with a web page and the time when the browser's main thread is able to start processing that interaction event. When a user interacts with a web page, an event is added to a queue to be processed by the browser's main thread. However, if the main thread is already busy doing other tasks like parsing HTML, executing JavaScript, or handling other event listeners, the new event has to wait in the queue. The FID metric captures the duration of this waiting time, which tells us how long it takes for the browser to respond to the user's first input while the main thread is busy.…