INP (Interaction to Next Paint)
Interaction to Next Paint measures the responsiveness of your page to user interactions — clicks, taps, and keyboard input. It replaced FID (First Input Delay) as a Core Web Vital in March 2024. An INP under 200 milliseconds is "Good."
Why It Matters for Shopify Stores
INP measures how quickly your store responds when a shopper interacts — tapping a product variant, clicking 'Add to Cart', or filtering a collection. A high INP score means shoppers experience noticeable lag after tapping, which is particularly damaging on mobile. Heavy JavaScript from third-party apps (review widgets, chat tools, loyalty programs) is the most common cause of poor INP on Shopify stores.
How to Check Your Store
Check INP in Google PageSpeed Insights under 'Core Web Vitals'. Use Chrome DevTools > Performance tab and interact with the page while recording to see which interactions are slow.
Use the free shopify app bloat calculator toolHow to Fix It
Break up long JavaScript tasks into smaller chunks. Defer non-critical third-party scripts. Remove or replace heavy apps that execute JavaScript on every page interaction.
Related Terms
LCP (Largest Contentful Paint)
Core Web VitalsLargest Contentful Paint measures how long it takes for the largest visible content element on a page — usually a hero image or headline — to finish loading.
CLS (Cumulative Layout Shift)
Core Web VitalsCumulative Layout Shift measures visual instability — how much page elements unexpectedly move while the page is loading.
FCP (First Contentful Paint)
Core Web VitalsFirst Contentful Paint marks the point when the browser first renders any text, image, or non-white content to the screen.
Unused App Scripts
ShopifyUnused app scripts are JavaScript files that load on every page of a Shopify store from apps that have been removed from the store admin but whose code remains in the theme.
Render-Blocking Resources
PerformanceRender-blocking resources are CSS or JavaScript files that prevent a browser from displaying page content until they've fully downloaded and parsed.
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