What is Interaction to Next Paint (INP)?
Interaction to Next Paint is a Core Web Vitals metric for responsiveness. It measures the delay between a click, tap or key press and the next frame the browser paints, across all interactions on a page, and reports one of the slowest. A result of 200 milliseconds or less is good.
What INP replaced
INP became a Core Web Vital in March 2024, replacing First Input Delay. First Input Delay measured only the first interaction and only the wait before processing started; INP covers every interaction, through to the visible response.
Why pages respond slowly
Long JavaScript tasks block the main thread, so the browser cannot react until they finish. Heavy third-party scripts, the cost of starting up JavaScript frameworks in the browser and expensive work inside event handlers are the usual causes.
How to improve it
Ship less JavaScript, split long tasks so the browser can respond between them, and load third-party tags after the page is usable. Frameworks that send little JavaScript by default, such as Astro, start from a strong position.
