Question 1

What are the mobile Core Web Vitals for developer.mozilla.org?

Accepted Answer

developer.mozilla.org mobile (phone form factor) p75 metrics from Google CrUX: LCP 1581ms (good), INP 126ms (good), CLS 0.000 (good). Mobile reflects real-world conditions for the ~60% of web traffic that's mobile-first.

Question 2

Why are mobile vitals usually worse than desktop for developer.mozilla.org?

Accepted Answer

Mobile devices have constrained CPU + RAM + cellular network conditions vs desktop's wired connection. Typical mobile shows 30-60% slower LCP + 40-70% higher INP than desktop on the same site. CLS varies less by device. Mobile is also Google's primary ranking signal — mobile vitals directly affect search rankings.

Question 3

How current is the mobile CrUX data for developer.mozilla.org?

Accepted Answer

Collection window: 2026-05-23 to 2026-06-19. Google CrUX publishes monthly aggregates derived from 28-day p75 trailing measurements of real Chrome users on phone devices. Refresh cadence is automated.