Speed reports are full of acronyms that hide simple ideas. There are only three that matter, and each corresponds to something a visitor physically experiences.
LCP — how long until the page looks loaded
The time until the largest thing on screen appears, usually a hero image or headline. Under 2.5 seconds is the target. It is nearly always fixed by making images smaller and loading them sooner.
INP — how quickly the page reacts when tapped
The delay between a tap and something visibly happening. Under 200 milliseconds. Poor scores usually mean too much JavaScript running on the main thread — often from third-party scripts nobody audits.
CLS — how much the page moves while loading
The layout shift that makes you tap the wrong button. Fixed by reserving space for images, ads and embeds before they arrive.
What to do about it
- Serve modern image formats at the size actually displayed.
- Audit third-party scripts — chat widgets and tag managers are frequent offenders.
- Set explicit dimensions on every image and embed.
- Measure with field data, not just a lab score on a fast laptop.
None of this is exotic. It is discipline applied during the build, which is why it costs almost nothing then and a great deal later.
