Search and the web
Three measurements of how a page feels to use — how fast the main content appears, how quickly it responds, and how much it moves while loading.
Also called LCP · INP · CLS
Formula
LCP ≤ 2.5 s · INP ≤ 200 ms · CLS ≤ 0.1
- LCP
- Largest Contentful Paint — when the biggest element in the viewport has rendered
- INP
- Interaction to Next Paint — the latency of the page's worst realistic interaction
- CLS
- Cumulative Layout Shift — how much content jumped without the user causing it
The thresholds are assessed at the 75th percentile of real visits, not in a lab. A site can pass every test on a developer's machine and fail the metric that is actually used.
These are field measurements collected from real browsers, which is why a lab tool disagreeing with the reported score is usually the lab tool being wrong about the audience. Devices and networks in the real distribution are slower than the ones sites are built on.
INP replaced First Input Delay in 2024 and is much harder to pass, because it measures every interaction rather than only the first, and it includes the time to render the response rather than only the delay before handling it.
A perfect synthetic score with a slow real-world 75th percentile is the common outcome of optimising the tool. Read field data, segment by device class, and fix the worst tenth rather than the median.
The definitions are the easy part. Whether the figure on your dashboard was computed this way is a different question, and usually the more expensive one.