Fluctuating PageSpeed Mobile Performance Scores for Next.js Project

Hello Vercel Team,

I hope you’re doing well. I wanted to report a strange behavior I’ve observed when testing my Next.js project (https://lp.roofworx.ai/) in PageSpeed Insights. On the desktop report, I consistently see a Performance score of 93. However, in the mobile report, the Performance score jumps around unpredictably—sometimes it’s as low as 71, other times 80, and occasionally it reaches 95.

To summarize:

  • Project: https://lp.roofworx.ai/ (Next.js, deployed on Vercel)
  • Desktop Performance: Stable at 93
  • Mobile Performance: Fluctuates between ~71, ~80, and ~95 across multiple test runs

These variations only occur in the mobile report; the desktop score remains steady. I have already checked my custom code, image optimizations, and analytics scripts, but everything appears correct on my end.

Could you please advise why the mobile Performance metric might be so inconsistent? Is it related to cold starts on the free Vercel plan or any other Vercel-specific behavior? Any insights or recommendations to stabilize the mobile score would be greatly appreciated.

Thank you for your time and assistance.

1 Like

Hey, thanks for posting!

I ran your site in the insights so i could see myself (here is the report I got).

It looks like your opening banner has a 5s LCP which is probably doing most of the weight in your lower score.

This is probably from testing on a slower connection on mobile (this report shows slow 4g throttling) and why the report wouldn’t be consistent.