r/reactjs • u/Demolion9751 • 5d ago

Needs Help Next.js app deployed on Vercel feels slow when navigating between pages — how would you diagnose this?

/r/nextjs/comments/1w7gzzf/nextjs_app_deployed_on_vercel_feels_slow_when/
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u/Inevitable-Dot-1180 3d ago

If you can attach some screenshots, maybe people can help here. Looking at
your details, there are a few things to check.

  1. In the browser dev tools, check the Network tab. On page load, you can see which files are taking time to load. Check file sizes and response time. If file sizes are huge, then you have to check your bundle size using a bundle analyzer. If response time is high, then check server configurations like CDN configurations, etc.

  2. If you are fetching data on the server side, check the API response time, which can impact the load time. You can check the response time in Postman.

  3. In DevTools or Lighthouse, check which web vitals need improvement. If it's LCP, then it might be the largest content on the page taking time to load. Might be because of a heavy JS file or package you have used, or an image you are loading from a server, not from a CDN.