Imagine a customer has found the right product. They've read the description, checked the price, and decided to buy.
They click “Add to Cart.”
Nothing happens.
They click again. They wait. They don't know whether the button worked, whether the product was added, or whether the page has frozen. Instead of completing their purchase, they have to guess what's happening.
Maybe they try one more time. Maybe they leave.
Not every slow interaction results in a lost sale, but an unresponsive website can turn a simple action into a frustrating experience. And when someone is ready to act, the last thing they need is a technical obstacle.
What does it mean when a website is slow to respond?
A website may appear to have loaded, yet still fail to respond quickly when someone clicks a button, opens a menu, selects an option, or adds a product to their cart.
Sometimes, the action appears not to have registered. Other times, the page updates after a delay. The user doesn't know whether to wait, click again, or give up.
This is where INP (Interaction to Next Paint), one of Google's Core Web Vitals metrics, comes in.
What is INP?
INP assesses how quickly a page responds to user interactions by measuring the delay between an interaction and the next visual update. It considers eligible interactions throughout a visit and generally reflects one of the slowest interactions, with certain statistical exceptions.
In simple terms, INP helps you understand whether a page responds promptly when people try to use it.
Google considers an INP of 200 milliseconds or less good. Values above 200 and up to 500 milliseconds need improvement, while values above 500 milliseconds are considered poor. The assessment is made at the 75th percentile of visits when sufficient data is available.
INP does not measure every aspect of website speed. For example, it is not the same as the page's initial loading time; LCP is the relevant metric for that.
Why does website responsiveness matter to your business?
1. A button that appears stuck creates doubt
When someone clicks “Submit Request” and sees no response, they don't know whether the form was sent. When they click “Add to Cart” and nothing visibly happens, they don't know whether the product was added.
Even if the system is processing the action in the background, a lack of visible feedback can make the experience confusing.
2. A simple action becomes extra work
Visitors came to find information, request a quote, or make a purchase. They didn't come to repeat clicks and check whether each action worked.
When a website doesn't respond promptly, users have to make extra effort. Some will continue; others may abandon the process.
3. Friction can affect conversions
A slow interaction can happen at a critical point in the customer journey: opening a menu, selecting an option, adding an item to a cart, or submitting a form.
If you notice a low conversion rate or abandonment at particular steps, it's worth reviewing the technical experience too. However, INP alone cannot explain business results. Your offer, pricing, trust signals, traffic, and purchasing process matter as well.
What can cause poor INP?
Several technical issues can affect INP, including:
- Long-running JavaScript. While the browser executes certain tasks, it may delay processing an interaction.
- Long tasks on the browser's main thread. These can prevent the page from responding promptly to clicks or taps.
- Too much code or third-party scripts. Analytics tools, widgets, chat tools, ads, and other scripts can add to the browser's workload.
- Slow interface updates. After an interaction, the page may take too long to display the change.
- Inefficient event handling. Code that handles clicks or input may do more work than necessary.
These are possible causes. Diagnosis should be based on page data and the interactions that are slow, rather than assumptions.
How can you check INP on your website?
Start with Google PageSpeed Insights. Enter your page URL and review the Core Web Vitals data when available.
Look at:
- Field data: aggregated information about real users' experiences, when sufficient data is available.
- Lab data and diagnostics: these can help identify long tasks and code that blocks the main thread, but they do not reproduce every real-world interaction.
- Important pages and actions: pay particular attention to forms, menus, filters, variant selectors, and purchase buttons.
If the issue occurs only on certain pages or devices, identify exactly where it happens. A single test cannot tell you everything about every visitor's experience.
What can you do to improve INP?
The right solution depends on the cause. Depending on the diagnosis, improvements may include:
- reducing unnecessary JavaScript;
- breaking long tasks into smaller tasks;
- delaying code that is not immediately necessary;
- reviewing third-party scripts and removing those that do not provide enough value;
- optimizing interface updates after a click;
- providing clear visual feedback, such as a loading state or confirmation after a form submission;
- testing again after changes to confirm that interactions have become faster.
Visual feedback does not replace performance optimization, but it helps users understand whether an action has been received. A button should clearly communicate what's happening without allowing accidental repeated submissions.
INP and SEO: what's the connection?
INP is one of the Core Web Vitals metrics, and Google ranking systems consider Core Web Vitals as part of page experience evaluation. However, a good INP score does not guarantee a particular Google ranking or an increase in conversions.
The practical value is more direct: a responsive website is easier to use. Improving interactions can remove technical obstacles from the user journey, while an SEO strategy must also account for relevance, content quality, and other factors.
Customers shouldn't have to wonder whether your website heard them
When a customer clicks a button, they should be able to understand quickly what happened. If they have to repeat the action or guess whether their form was submitted, the experience becomes harder than it needs to be.
INP helps measure one part of that experience. It cannot tell you on its own why people buy or leave, but it gives you a technical signal you can investigate.
It's not enough for a website to load. It also needs to respond when a customer is ready to act.
Want to find out why your website feels unresponsive?
Start by checking INP and the interactions that matter to your business, from forms to purchase buttons. Identify the issue before choosing a solution.
Frequently asked questions
What does INP mean?
INP (Interaction to Next Paint) measures how quickly a page responds to user interactions by assessing the delay until the next visual update.
What is a good INP score?
An INP of 200 milliseconds or less is considered good. Between 200 and 500 milliseconds needs improvement, while above 500 milliseconds is considered poor.
Why are the buttons on my website not responding?
Possible causes include long-running JavaScript, long tasks on the browser's main thread, third-party scripts, or slow interface updates. A technical diagnosis is needed to identify the exact issue.
Can INP affect conversion rate?
Slow interactions can create friction at important steps, such as submitting a form or adding a product to a cart. However, conversion rate depends on many factors, and INP alone does not explain the results.
How can I check INP?
Use Google PageSpeed Insights to review Core Web Vitals data when available and investigate the performance recommendations.
Read next
- Your Website Is Losing Customers Without You Realizing It. Here's Why.: Core Web Vitals and user experience.
- How Much Do Those Waiting Seconds Cost You?: LCP and main-content loading.