Interaction to Next Paint (INP)
Interaction to Next Paint measures how quickly a page reacts when a visitor does something: taps a button, clicks a link, opens the menu, types into a field. It’s the time from the interaction until the screen shows a response. A visitor taps “Add to cart”, and for half a second nothing seems to happen. INP measures that half second.
INP is one of the three Core Web Vitals.
Why it matters
Section titled “Why it matters”When a page doesn’t react right away, visitors tap again, assume it’s broken or leave. A quick visible response, even only a button changing color, tells them the page got the message.
INP looks at all the clicks, taps and key presses during a visit and reports one of the slowest. On pages with very many interactions, it ignores the odd outlier. Scrolling and hovering don’t count. INP replaced First Input Delay (FID), which only measured the wait before the first interaction.
INP needs real people doing real things, so it comes from field data only. When no one interacted with a page during the 28 days, or not enough Chrome visitors did, there’s no value. In the lab test, Total Blocking Time gives a hint instead.
What influences it
Section titled “What influences it”An interaction has three parts: the wait until the browser starts handling it, the time the page’s code takes to respond, and the time until the next frame is drawn.
Browser: The most common cause of a poor INP on WordPress sites is a browser that’s busy with other scripts when the visitor taps. Analytics, ads, chat widgets and tracking keep running after the page has loaded, and a tap has to wait until they’re done. A very large page, with thousands of nested elements, makes every update of the screen slower.
WordPress: Themes and plugins decide what happens on each interaction. Mega menus, filters, search suggestions, form validation and “add to cart” buttons that update the page with JavaScript can do a lot of work for a single tap.
Cache: Returning visitors with cached scripts skip the download, but the work of running the code stays the same.
In Permo
Section titled “In Permo”Permo shows INP in the Real users section of its PageSpeed page, marked as a Core Web Vital: the value that 75% of Chrome visits reached or beat over the last 28 days. There’s no lab value, because the test doesn’t interact with the page.