PERF-006
Heavy JavaScript payload
LowDefault severity · Performance · SEO, quality and performance
Last reviewed
What it checks
Total size of the same-site JavaScript files the page loads (up to 15 files).
Why it matters
Large bundles delay interactivity on mid-range phones even when the network is fast.
Recommended fix
Code-split routes, lazy-load heavy components and remove unused libraries.
How to verify
Compare total JS in DevTools → Network (JS filter) before and after; aim for under 500 KB compressed.
Example fix prompt
Generic prompt (your report adds the evidence)
Please fix this production issue in my app.
Issue PERF-006: Heavy JavaScript payload
Site: https://your-app.example
First confirm the issue in the code or live config. If it is not present, say so and change nothing.
Task: Reduce the JavaScript the homepage loads: lazy-load heavy components that are not visible on first paint (charts, editors, 3D, maps), split code per route, and remove or replace large unused dependencies. Show me the biggest chunks before and after.
Constraints: make the smallest change that fixes this, keep the current design and behaviour, never paste secret values into code or chat, and tell me which files you changed.
Done when: Compare total JS in DevTools → Network (JS filter) before and after; aim for under 500 KB compressed.