First Input Delay / INP
TL;DR
INP (replacing FID) measures how fast your page responds to user interactions — clicks, taps, key presses. Under 200ms is good; slow interactivity drives users away.
Explain Simply
INP is like pressing an elevator button. If nothing happens for a few seconds, you press it again and again. A fast website responds instantly to every button press.
FID measures the delay from when a user first interacts (click, tap) to when the browser responds. FID reflects page responsiveness. Good threshold: ≤100ms. FID is being replaced by INP (Interaction to Next Paint) since 2024.
INP measures the latency of every interaction, not just the first one. It takes the worst interaction (or near-worst for pages with many interactions) as the page's INP score. Good threshold: ≤200ms, needs improvement: 200-500ms, poor: >500ms.
Poor INP is usually caused by heavy JavaScript: long tasks blocking the main thread, synchronous API calls, expensive DOM manipulations, and third-party scripts. Solutions: break long tasks into smaller chunks (yield to main thread), use web workers for heavy computation, defer non-critical JS, and reduce third-party script impact.
⚡Why It Matters
Web pages must respond quickly to user interaction. Poor FID/INP is usually caused by heavy JavaScript blocking the main thread. Google found that improving INP from poor to good correlates with 22% fewer page abandonments.
🔍How AiSEO Checks
AiSEO measures FID/INP via CrUX data and Lighthouse, detects long tasks blocking the main thread, and suggests code splitting and deferring non-critical JS.
AiSEO Score Impact
Up to 3 points in the Performance category (15% of total score)
Fix Difficulty
Editor: N/A | Developer: Hard | AI Agent: Medium