What is INP by on-page errors
INP by on-page errors shows how Interaction to Next Paint (INP) varies depending on whether the page encountered any loading errors — such as JavaScript exceptions, broken assets, missing fonts, or failed CSS files.
Even though INP focuses on interactivity, early-stage errors can ripple through the runtime lifecycle. This lens reveals how error-prone pages may degrade responsiveness — often in ways that aren’t immediately obvious.
Healthy INP by on-page errors sample
Should you worry
In a healthy state:
“No errors” sessions show fast (green) INP values
Any sessions with errors are rare, and don’t significantly degrade responsiveness
JavaScript failures don’t block hydration or delay event listeners
The main thread remains free enough to handle input quickly, even in the presence of minor issues
This means your site is both functionally robust and resilient under failure, which is essential for consistent interactivity.
Unhealthy INP by on-page errors sample
If INP is noticeably worse when on-page errors occur, it often means:
A failed script broke hydration or delayed interactive components from being wired up
An error triggered a fallback state or retry mechanism that introduced additional JS work during idle time
The user clicked or tapped during a long error-handling routine — resulting in jank or input delay
There’s poor error boundary coverage in your framework (especially common in SPAs)
INP degradation due to errors is a strong sign your site is tightly coupled to fragile resources or brittle runtime paths.
Resolving unhealthy INP by on-page errors
Go-to action plan to resolve an unhealthy INP by on-page errors:
Ask Uxi to analyze your INP by on-page errors values and suggest improvements.
Use Filters to isolate slow INP sessions and correlate them with broken assets or JS error logs.
Simulate INP of the suspected lens to see if fixing it will resolve the INP by on-page errors. If yes, this is where the resolution focus should be.
Use an automated INP optimization tool like INProve to improve your INP by on-page errors values.
Once you’ve improved INP, set an alert to be the first to know if it starts worsening again.
Try it yourself
Discover how your website performs with real user data.