What is LCP by on-page errors
LCP by on-page errors tracks how Largest Contentful Paint (LCP) varies depending on whether the page encountered errors during loading - and if so, what kind.
These errors may include JavaScript failures, broken image loads, font problems, CSS issues, or even unknown sources. The presence of any on-page error can slow down rendering or degrade the user experience in subtle ways - especially if the error affects a critical resource or blocks rendering.
This view helps identify whether poor LCP is directly correlated with unstable or error-prone page behavior.
Healthy LCP by on-page errors sample
Should you worry
A healthy chart shows "No errors" dominating with fast (green) LCP values - and ideally, other error types are either missing entirely or show up with low volume and no impact on performance.
This means:
Your site loads predictably and reliably.
Critical content isn’t blocked or delayed due to broken resources.
JavaScript failures aren’t interfering with layout or hydration.
Bonus points if even the rare error cases don’t introduce rendering delays - it means you're error-resilient.
Unhealthy LCP by on-page errors sample
When LCP is significantly worse on pages with errors, it usually means:
A broken resource is delaying or preventing the largest element from rendering - for example, a hero image failing to load.
JavaScript errors are interrupting hydration or client-side rendering.
Fonts or CSS not loading correctly, leading to FOUT/FOIT or delayed layout shifts.
The most common pattern? LCP element is directly tied to a resource that failed to load or execute - dragging down performance, even when the rest of the page is fine.
Worse still, users might see content pop in late, unstyled, or not at all — especially if fallback strategies are missing.
Resolving unhealthy LCP by on-page errors
Go-to action plan to resolve an unhealthy LCP by on-page errors:
Ask Uxi to analyze your LCP by on-page errors values and suggest improvements.
Use Filters to focus on sessions with specific errors and check which pages, layouts, or assets are consistently causing issues.
Simulate LCP of the suspected insight to see if fixing it will resolve the slow LCP by on-page errors. If yes, this is where the resolution focus should be.
Use an automated LCP optimization tool like Navigation AI to improve your LCP by on-page errors values.
Once you’ve improved LCP, 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.