Direct Answer
Aim for Largest Contentful Paint under 2.5 seconds, First Input Delay under 100ms, and Cumulative Layout Shift under 0.1 — Google's Core Web Vitals thresholds. On 4G mobile, total page weight should be under 1.5 MB and Time to Interactive under 3.8 seconds.
Short version
“A fast website loads in under two and a half seconds with stable layout. That meets Google's Core Web Vitals.”
Portent's 2022 study of 27 billion sessions found conversion drops 4.42% for every additional second of load time between 0 and 5 seconds.
53% of mobile users abandon a site that takes longer than 3 seconds to load (Google/SOASTA mobile speed benchmark).
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