What is Interaction to Next Paint (INP)?
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INP (Interaction to Next Paint) is a Core Web Vital that measures how quickly a web page responds to a user’s interactions — clicks, taps, and key presses — throughout the entire visit. Specifically, it captures the delay between an interaction and the moment the page visually updates in response. A low INP means the page feels instantly responsive; a high one means it feels sluggish and laggy.
INP replaced FID (First Input Delay) as a Core Web Vital in March 2024, and it’s a stricter measure. Where FID only looked at the first interaction and just the input delay, INP evaluates all interactions across the visit and measures the full time until the next paint — so it reflects real, ongoing responsiveness rather than a single first impression. The thresholds are:
- Good — 200ms or less
- Needs improvement — 200ms to 500ms
- Poor — over 500ms
High INP is almost always a JavaScript problem. When a user interacts, the browser’s main thread may be busy running scripts, so it can’t update the page until that work finishes. Long tasks, heavy event handlers, and large frameworks all block the main thread and push INP up — which is why interaction-heavy pages like faceted category listings are the usual offenders.
On Magento (Adobe Commerce), INP is frequently the hardest Core Web Vital to pass, because the legacy RequireJS/Knockout frontend runs heavy JavaScript exactly where users interact — filters, search, add-to-cart. Fixes include reducing and deferring JavaScript, breaking up long tasks, and full-page caching; the structural fix is a lightweight frontend like Hyvä, which strips out the heavy legacy stack and lets most stores hit a green INP score without endless patching.
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