Key Takeaways
- INP (Interaction to Next Paint) measures how quickly your page responds when someone taps or clicks. A good score is 200 milliseconds or less.
- INP replaced FID as a Core Web Vital on 12 March 2024, and it is a much harder test because it measures almost every interaction, not just the first.
- Across the web, only 48% of mobile sites passed all three Core Web Vitals in 2025, and mobile responsiveness is the area with the widest gap between phones and desktops.
- Most INP failures come from heavy JavaScript, too many third-party scripts, and bloated plugins, not from your images or your hosting alone.
- A slow, janky page costs you customers before it ever costs you rankings, because 53% of mobile visits are abandoned when a page takes longer than three seconds.
Most website owners have heard of page speed, but far fewer have heard of INP, and it is the Core Web Vital that quietly trips up the most sites once people start tapping and clicking. Google's own research found that 53% of mobile visits are abandoned if a page takes more than three seconds to load, and a page that feels slow to use does the same kind of damage even after it has loaded.
This guide explains what INP is in plain English, why so many sites struggle with it, what a good score looks like, the most common causes, and the practical fixes that actually move the number. No jargon for its own sake, just what a non-technical business owner needs to know.
What INP actually measures
INP stands for Interaction to Next Paint. In plain terms, it measures the gap between someone interacting with your page, a tap, a click, a key press, and the moment the screen visibly updates in response.
Think of tapping "Add to basket" and waiting half a second before anything happens. That pause is what INP captures. A snappy page responds almost instantly, and a sluggish one leaves people wondering whether their tap even registered.
Google's threshold for a good experience is clear. According to Google's own guidance on INP, a good score is 200 milliseconds or less, anything between 200ms and 500ms needs improvement, and above 500ms is poor.
Why INP replaced FID, and why it is harder
Until March 2024, the responsiveness metric was FID, or First Input Delay. FID only looked at the delay on the first interaction someone made, which was a fairly easy bar to clear.
INP is different. It looks at the responsiveness of nearly every interaction across the whole visit and reports a value that most of them sit beneath. The switch became official on 12 March 2024, and a lot of sites that quietly passed FID suddenly had a real problem to solve.
The pattern across the web is telling. The 2025 Web Almanac found that only 48% of mobile sites passed all three Core Web Vitals, and responsiveness on mobile shows the widest gap between phones and desktops of any of the three metrics. In short, the page that feels fine on your office laptop can feel sluggish on a customer's mid-range phone.
The most common reasons sites fail INP
If your INP is poor, the cause is usually one or more of these. We see the same culprits again and again.
- Too much JavaScript: the browser can only do one thing at a time on the main thread. While it is busy running scripts, it cannot respond to a tap, so the more code there is, the longer people wait.
- Third-party scripts you forgot about: live chat widgets, analytics, heatmaps, cookie banners, ad tags, and social embeds all run code on your visitor's device. Each one is small on its own, and together they choke responsiveness.
- Bloated plugins and page builders: on many WordPress sites the theme and a stack of plugins load far more than the page needs, which is one of the biggest hidden drags on interactivity.
- Heavy work on interaction: if tapping a filter or opening a menu triggers a lot of calculation, the screen cannot repaint quickly, and INP suffers.
- Cheaper devices: your visitors are not all on the latest phone. Lower-powered devices process the same code more slowly, so a page that is borderline on a flagship can fail badly on a budget handset.
How to fix a poor INP score
The good news is that INP is fixable, and the fixes also tend to make the whole site faster. Here is the order we usually work in.
- Cut the JavaScript you do not need: the single most effective change is shipping less code. Remove unused scripts, retire plugins you no longer rely on, and question every new tag before you add it.
- Defer and split what is left: code splitting and deferring non-essential scripts means the browser loads what the page needs first and the rest later, so interactions stay responsive. This is standard practice on a modern build.
- Audit your third-party scripts: list every external script on the page and justify each one. Many businesses are carrying tags from tools they stopped using months ago. Our website audit and consultation service exists largely to find these.
- Consider a faster build: if your site is a tangle of plugins on a slow theme, patching it has limits. A lean, modern build often clears the Core Web Vitals comfortably. We cover when that is worth it in our guide on whether a WordPress rebuild is worth it for SEO and Lighthouse.
- Get specialist help if the fixes stall: if you have trimmed the obvious things and the score is still poor, focused website speed optimisation work on the code itself is usually what is needed.
In our work rebuilding and tuning sites for UK businesses, the pattern is consistent. The number rarely improves from a single quick fix, but it moves a lot once you treat script bloat seriously across the whole site.
How to check your INP
You do not need to guess. Two free Google tools tell you where you stand.
- PageSpeed Insights: paste in any page URL and you get both lab data and real-world field data from the Chrome User Experience Report. The field data is what matters, because it reflects what your actual visitors experience.
- Search Console Core Web Vitals report: this groups your pages into good, needs improvement, and poor, based on real visitor data across the whole site, so you can see how widespread a problem is.
If you want the wider context on speed and rankings, our guide on why your website is slow and the speed fixes that affect Google rankings is a good companion read, and our explainer on how to improve your Lighthouse score to boost SEO covers the wider scoring picture.
Frequently Asked Questions
What is a good INP score? A good INP score is 200 milliseconds or less. Between 200ms and 500ms needs improvement, and anything above 500ms is poor. The full set of good Core Web Vitals targets is LCP at 2.5 seconds or under, INP at 200ms or under, and CLS at 0.1 or under.
What is the difference between INP and FID? FID, the old metric, only measured the delay on the very first interaction a visitor made. INP measures the responsiveness of nearly every interaction across the whole visit, so it is a far harder and more honest test of how a page actually feels to use. INP replaced FID as a Core Web Vital on 12 March 2024.
Why does my website fail INP? INP problems are almost always caused by heavy JavaScript and too many third-party scripts. When someone taps a button, the browser has to finish its current work before it can respond, so chat widgets, analytics tags, ad scripts, and bloated plugins all add up to a sluggish feel. Older or cheaper phones make it worse because they have less processing power.
How do I check my INP score? Use Google PageSpeed Insights for a quick read on a single page, and the Core Web Vitals report in Google Search Console for site-wide data based on real visitors. PageSpeed Insights shows both lab data and field data from the Chrome User Experience Report, and the field data is what Google actually uses.
Does INP affect my Google rankings? Yes, INP is one of the Core Web Vitals that feed into Google's page experience signals. It is not the single biggest ranking factor, but when two pages are close on relevance, a faster and more responsive page has the edge. The bigger win is usually commercial, because a responsive page keeps more visitors and converts more of them.
The Bottom Line
INP is the Core Web Vital that reflects how your site actually feels to use, and that is exactly why interaction-heavy sites struggle with it. The causes are rarely mysterious, heavy JavaScript, forgotten third-party scripts, and bloated plugins do most of the damage, and the fixes pay off twice, once in Google's page experience signals and again in visitors who stay and buy. Check your score, treat script bloat as a real problem, and decide honestly whether your site needs tuning or a cleaner build.
If your scores are stuck in the red and you want a clear picture of what is causing it, get in touch for a straight answer. We can run website speed optimisation on the code that is slowing you down, or take a wider look across the whole stack as part of our web development and UX work.
