Check Core Web Vitals.
Pass the test.

The three metrics, their thresholds, and what breaks them

Core Web Vitals are three specific measurements with published thresholds. Knowing the exact numbers matters, because "needs improvement" and "poor" are not the same conversation.

Largest Contentful Paint (LCP) measures when the biggest thing in the viewport finished rendering, which is a good proxy for "the page looks ready". Good is 2.5 seconds or under. Poor is over 4 seconds. It is usually broken by a slow server response, a hero image that is not preloaded, or render-blocking resources ahead of it in the queue.

Interaction to Next Paint (INP) measures responsiveness across the whole visit, taking close to the worst interaction rather than the first. Good is 200 milliseconds or under. Poor is over 500 milliseconds. It replaced First Input Delay in March 2024, and the change was significant: FID only measured the delay before processing started, which flattered pages that accepted a click instantly and then froze. INP measures through to the next paint, so long JavaScript tasks that block the main thread now show up honestly.

Cumulative Layout Shift (CLS) measures how much visible content jumps around without the user causing it. Good is 0.1 or under. Poor is over 0.25. It is almost always images or ad slots without reserved dimensions, fonts that reflow text when they swap in, or content injected above what someone is already reading.

The detail most checkers skip

All three are assessed at the 75th percentile of page loads, not the average. That choice is deliberate and it changes how you should read your own data. It means a quarter of your visits can be worse than your reported score and you still pass. It also means an average that looks healthy can hide a slow tail that fails, which is common when a minority of your audience is on older devices or weaker networks.

Field data also moves on a rolling 28-day window, so a fix you shipped this morning will not show up for weeks. Use lab tools to confirm the fix worked, and field data to confirm it mattered.

How UtilitySEO handles this

The audit surfaces the underlying causes rather than only the three headline numbers, because "LCP is 4.1s" is a symptom and the fix list needs to name the resource responsible. Results cover mobile and desktop separately, since the two frequently disagree and mobile is the one that usually needs work.