Speed is part of the design
A fast first impression, stable layout and immediate response determine whether an interface feels reliable. Performance should never be postponed until the final week of testing.
Budget before effect
Large images, fonts, tracking and WebGL receive a budget in advance. An interaction that slows the primary task is not finished.
- LCP below 2.5 seconds
- INP below 200 milliseconds
- CLS below 0.1
- Test on real mobile hardware
Measure after launch
A lab test is the start. Field data shows how real visitors, devices and connections experience the site.
Assess LCP, INP and CLS at the 75th percentile and separate mobile from desktop. This prevents a fast office device from masking the experience on slower phones.
Primary sources
The factual and technical claims in this article were checked against these sources.
