ChunkLoadError Cache Checker
ChunkLoadError: Loading chunk 5760 failed after a deploy means a browser asked for a hashed file your new build no longer has. The headers tell you why it asked. Paste the curl -I output of a page and of one chunk.
Runs entirely in your browser — nothing you paste is sent anywhere. Cookie values, Authorization and token-like URL parameters (query and fragment) are masked in the output.
curl -sI https://your-site.com/some-page
curl -sI https://your-site.com/_next/static/chunks/…js
Take the chunk URL from the error itself (Loading chunk 5760 failed. (error: https://…)) or from DevTools → Network, filtered on _next/static. curl -v and curl -L output work too.
What gets checked
HTML cached past a deploy
max-age, Expires or Last-Modified heuristics on the page, immutable, s-maxage with a CDN in front, and cache hits or cache-eligible HTML reported by cf-cache-status, x-vercel-cache, Cache-Status or Age
Chunk gone (404 / 410)
the version skew Next.js documents — including a 404 that Cloudflare itself cached
Chunk refused (401 / 403 / 429)
auth or deployment protection in front of static files, and the 403 that S3 returns for a missing object
CSS chunk with the wrong type
a stylesheet not served as text/css fails in the browser, with or without nosniff
Chunk answered with HTML
a single-page-app fallback or catch-all rewrite returning your page instead of a 404
Chunk redirected
auth logic in proxy/middleware whose matcher does not exclude _next/static
Mismatched deployment ids
x-nextjs-deployment-id on the page against the ?dpl= of the chunk
Service worker cache
what curl cannot see: a worker answering navigations from the Cache API
Chunk not immutable
a performance cost, reported as such — it is not what causes the error
Every rule is checked against the Next.js, Cloudflare, Vercel, Netlify, nginx, MDN and RFC documentation; each finding links its source.
Headers clean, error still there?
Then it is usually tabs opened before the deploy (fixed by deploymentId), rolling deploys with mismatched build IDs, or a standalone build missing .next/static. The full breakdown covers all five causes, with the decision table.
Step-by-step fixes for these errors
This tool runs on dev-error-explainers, an open-source, zero-dependency library — view the source on GitHub.