Interaction to Next Paint (INP) measures how responsive your website feels to user input. Learn how this Core Web Vital affects your Google rankings and visitor frustration.
Google updated its Core Web Vitals in 2024 to include a new metric called Interaction to Next Paint (INP). While previous metrics focused mainly on how fast a page loads, INP focuses on how fast a page reacts once a user is actually on it. If a customer clicks a button, opens a menu, or types in a search bar, they expect an immediate visual response. If the site hangs or stutters, your INP score suffers.
For business owners, a poor INP score is a silent killer. It represents a website that looks finished but feels broken, leading to high bounce rates and lower search rankings.
Defining Interaction to Next Paint
INP is a metric that tracks the latency of all interactions a user has with a page during their entire visit. It records the time between a user action, like a click or a keypress, and the very next time the browser is able to paint a frame on the screen showing the result of that action.
Unlike its predecessor, First Input Delay (FID), which only measured the very first interaction, INP looks at the worst-case scenario throughout the entire session. Google chooses the longest delay (or a representative high percentile for long sessions) to determine the score.
What Makes a Good INP Score?
To provide a good user experience, your website should respond to inputs in under 200 milliseconds. Google categorizes the scores as follows:
- Good: 200 milliseconds or less.
- Needs Improvement: Between 200 and 500 milliseconds.
- Poor: Greater than 500 milliseconds.
When a site hits the poor category, users begin to perceive the interface as laggy or unresponsive. In many cases, they will click a button multiple times, assuming the first click didn't work, which only adds more stress to the browser and worsens the delay.
The Three Components of Interaction Latency
The delay measured by INP is actually the sum of three distinct phases. Improving your score requires identifying which phase is causing the bottleneck.
Input Delay
This is the time the browser spends waiting to start handling the interaction. This usually happens because the browser’s main thread is busy processing a massive JavaScript file or a background task, forcing the user's click to wait in a queue.
Processing Time
This is the time it takes for the website's code to run in response to the input. For example, if a user clicks a Filter button on an e-commerce site, the processing time is how long it takes the code to calculate which products to show.
Presentation Delay
Once the code has finished running, the browser still needs to recalculate the layout and draw the new pixels on the screen. If the page is visually complex or has too many elements, this final step can cause a significant hang.
Why Heavy Websites Struggle with INP
The biggest culprit for high INP scores is excessive JavaScript. Traditional site builders and bloated platforms like WordPress often load dozens of scripts in the background for tracking, ads, and animations.
When a user tries to interact with a page while these scripts are running, the browser becomes paralyzed. It cannot respond to the user until it finishes the current task. Static websites and headless architectures have a natural advantage here because they ship significantly less code to the browser, keeping the main thread clear and ready to respond instantly.
Improving Your INP Score
Fixing INP is about prioritizing the user over background tasks.
- Break Up Long Tasks: If a script takes longer than 50 milliseconds to run, it should be broken into smaller chunks so the browser can pause to handle a user click in between.
- Remove Unused JavaScript: Every third-party plugin or tracking pixel you add increases the chance of an input delay. Audit your scripts and remove anything that isn't providing direct business value.
- Simplify the DOM: A website with thousands of nested elements is harder for the browser to repaint. Keeping your design clean and your code lean reduces the presentation delay.
The One Clear Takeaway: INP measures the gap between a user's action and the website's reaction. To rank well and keep customers engaged, your site must stay responsive long after the initial page load by keeping the browser's workload light.
