Interaction to Next Paint (INP)

The page responds to user interactions in under 0.2 seconds.

On this page

    Impact

    ScanGov impact ratings

    About

    Interaction to Next Paint (INP) measures how quickly a webpage responds to user actions like clicks or typing. It tracks the time from when you interact until the next screen update. A good INP score is 200 milliseconds or less, ensuring a smooth experience. INP has replaced First Input Delay (FID) as a key performance metric.

    Risks

    Site feels frozen when users click things.

    Why it's important

    A fast response time increases interactivity and user satisfaction, leading to a more engaging experience.

    User stories

    As a user interacting with the page, I want the site to respond quickly to my actions so that I feel in control and don't experience delays.
    As a user of a cheaper model mobile phone, I want your website to respond to my interactions quickly. If it is inefficient and performs a lot of processing on my device I wonder if it is even working, get stressed out and may click multiple times.

    Code

    Failing pattern:

    // Fail: long-running synchronous work on the main thread
document.getElementById("btn").addEventListener("click", () => {
  heavyComputation(); // blocks the main thread
});

    Passing pattern:

    // Pass: defer heavy work off the main thread
document.getElementById("btn").addEventListener("click", () => {
  setTimeout(() => heavyComputation(), 0);
});

    Error

    ScanGov messaging when a site fails a standard:

    Page response exceeded 0.2 seconds.

    Guidance

    Indicators

    On this page