What is the difference between INP and FID?

FID (First Input Delay) only measured the delay before the browser started processing the very first interaction on a page. INP measures the full latency — from input to the next visual update — for every interaction throughout the entire page lifecycle, then reports the worst (or near-worst) one. INP is therefore a much more comprehensive and realistic metric.

INP Interaction to Next Paint: The Core Web Vital to Master in 2025

Q: What is a good INP score?

According to Google, a good INP score is 200 milliseconds or less. Scores between 200 ms and 500 ms need improvement, and anything above 500 ms is considered poor. Most sites should aim to stay well below the 200 ms threshold for optimal user experience and SEO benefit.

What Is INP (Interaction to Next Paint)?

INP — short for Interaction to Next Paint — is the Core Web Vital metric that measures how fast your website visually responds to user interactions. Clicks, taps, key presses: every single one is tracked throughout the user’s visit, and Google uses the slowest (or near-slowest) interaction as your INP score.

In March 2024, Google officially replaced FID (First Input Delay) with INP in its Core Web Vitals. If you haven’t adjusted your optimization strategy yet, 2025 is the year to catch up.

Why Did Google Replace FID With INP?

FID had a major blind spot: it only measured the delay before the browser started processing the first interaction. It ignored everything that happened after — rendering, layout shifts, paint — and it completely ignored every subsequent interaction.

INP fixes all of that:

It measures the full round-trip from user input to the next frame painted on screen.
It tracks every interaction, not just the first one.
It reports the worst-case scenario (technically the 98th percentile), giving a realistic picture of responsiveness.

In short, a page could score a perfect FID of 10 ms but still feel sluggish throughout the session. INP catches what FID missed.

What Is a Good INP Score?

Google defines three thresholds:

Rating	INP Score
Good	≤ 200 ms
Needs Improvement	200 – 500 ms
Poor	> 500 ms

According to data from the Chrome User Experience Report (CrUX), roughly 65% of origins currently meet the “good” threshold. That means about one-third of all websites still have work to do — and that gap represents a real competitive SEO advantage for those who optimize.

Common Causes of Poor INP

Heavy JavaScript Execution

Long-running JavaScript tasks (over 50 ms) block the main thread and delay visual feedback. Third-party scripts — analytics, chat widgets, ad tags — are frequent offenders.

Unoptimized Event Handlers

Complex logic running synchronously inside click or keydown handlers can push response times well above 200 ms. A single poorly written dropdown menu can tank your entire INP score.

Excessive DOM Size

Pages with more than 1,400 DOM elements (Google’s recommended limit) force the browser to spend more time on layout recalculations and paint operations after each interaction.

How to Optimize INP: Practical Steps

Here are actionable techniques that deliver real results:

Break up long tasks using setTimeout, requestAnimationFrame, or the newer scheduler.yield() API so the browser can process user input between chunks of work.
Defer non-critical JavaScript with async or defer attributes, and lazy-load third-party scripts.
Minimize DOM complexity — audit your templates, remove unnecessary wrappers, and virtualize long lists.
Use CSS content-visibility: auto to skip rendering of off-screen elements.
Debounce or throttle expensive event handlers (scroll, resize, input) so they don’t fire on every frame.
Audit third-party scripts ruthlessly. At Lueur Externe, we regularly find that removing or deferring just two or three third-party tags can cut INP by 40-60%.

Measuring INP

You can measure INP using:

Google PageSpeed Insights (field data from CrUX)
Chrome DevTools → Performance panel (lab testing)
Web Vitals JavaScript library (web-vitals npm package) for real-user monitoring
Google Search Console → Core Web Vitals report for site-wide trends

Always prioritize field data (real users) over lab data. INP varies enormously depending on the device — a budget Android phone can produce INP scores 3-5x higher than a desktop machine.

Why INP Matters for SEO in 2025

Core Web Vitals are a confirmed Google ranking signal. While content relevance still dominates, page experience acts as a tiebreaker between competing pages. In crowded niches — e-commerce, SaaS, local services — a 100 ms INP improvement can mean the difference between position 5 and position 3.

Beyond rankings, fast interactions directly impact conversion rates. Research from Akamai shows that a 100 ms delay in responsiveness can reduce conversions by up to 7%.

Conclusion: Don’t Sleep on INP

INP is not a vanity metric. It reflects how your users actually experience your site — every click, every tap, every keystroke. With Google now using it as an official ranking signal, ignoring INP in 2025 means leaving both user satisfaction and search visibility on the table.

Whether you run a PrestaShop store, a WordPress site, or a custom web application, optimizing INP requires a blend of front-end expertise, performance auditing, and infrastructure know-how. That’s exactly what the team at Lueur Externe — certified PrestaShop experts, AWS Solutions Architects, and SEO specialists based in the Alpes-Maritimes — delivers every day.

Ready to improve your INP and climb the rankings? Get in touch with Lueur Externe for a free performance audit.