This translation has not been editorially reviewed yet. The German version is authoritative. Deutsche Fassung →
Checking INP: how fast a page responds to input
Interaction to Next Paint measures how long it takes for a page to visibly respond to an input — across all interactions in a visit, not just the first. It's the value that puts "the page is stuck" into a number.
- INP is the most awkward of the three core values, because it doesn't arise during loading but during use. Optimisations to the loading process often don't improve it at all.
- The cause is almost always the same mechanism: a long script section blocks the main thread, and everything else waits. Blocking time from the lab run shows how strongly this pattern shows up.
- Pages with many embedded third-party scripts are especially affected — each one brings its own work onto the same thread.
