ChunkLoadError: Loading chunk 4512 failed. (missing: https://example.com/_next/static/chunks/4512-a1b2c3d4.js)

Next.js · updated 2026-11-04

Thrown in the browser by the webpack runtime when a lazily loaded chunk fails to load: "missing" means the request completed but the file wasn't there (a 404 after a deploy), "timeout" and "error" mean the request itself failed. It surfaces in the browser console and in client-side error tracking, not in server logs.

ChunkLoadError: Loading chunk 4512 failed.
(missing: https://example.com/_next/static/chunks/4512-a1b2c3d4.js)
    at __webpack_require__.f.j (https://example.com/_next/static/chunks/webpack-8f2c.js:1:3912)
    at https://example.com/_next/static/chunks/webpack-8f2c.js:1:1311

Quick fix

If it follows deploys and says missing, the old HTML is asking for chunk files the new build replaced. Set a deploymentId per deployment so Next.js reloads the page when the deployment changes, keep the previous build's /_next/static files available for a while, and as a fallback reload once when a ChunkLoadError is caught. If it says timeout or error, look at the network: blocked requests, a CDN problem or flaky mobile connections.

1. Look at the part in parentheses: missing (file gone, usually a deploy) vs timeout or error (network).
2. Set deploymentId (or NEXT_DEPLOYMENT_ID) to a per-deploy value so mismatched clients do a full reload.
3. Keep old /_next/static files for at least a few hours after a deploy (most CDNs and object storage can keep them).
4. Don't cache HTML pages long at the CDN: cached HTML points at chunk files that no longer exist.
5. Fallback: catch ChunkLoadError in an error boundary or window error handler and reload the page once.

// app/error.tsx (route error boundary): reload once on a stale chunk
'use client';

export default function ErrorBoundary({ error }: { error: Error & { digest?: string } }) {
  if (typeof window !== 'undefined' && error.name === 'ChunkLoadError' && !sessionStorage.getItem('chunk-reload')) {
    sessionStorage.setItem('chunk-reload', '1');
    window.location.reload();
    return null;
  }
  return <p>Something went wrong. Please reload the page.</p>;
}

Why it happens

Other fixes

• CSS chunks fail the same way with "Loading CSS chunk … failed".
• Report these with the deployment ID attached so you can tell skew from real breakage in your error tracker.

Same error, other wording

• ChunkLoadError: Loading chunk 123 failed. (timeout: https://example.com/_next/static/chunks/123.js)
• Loading CSS chunk 456 failed.
• ChunkLoadError: Loading hot update chunk app/layout failed.

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References: Next.js docs: deploymentId (version skew), webpack source: the ChunkLoadError message