Next.js “Error: Body exceeded 1 MB limit” in a Server Action form

What happened on our test

On 16.10.2026 we built a form with an email field and a file input, handled by a Server Action through useActionState, on Next.js 16.4.2 in production mode. With a 2 MB file the server log printed:

Error: Body exceeded 1 MB limit. To configure the body size limit for Server Actions, see: https://nextjs.org/docs/app/api-reference/next-config-js/serverActions#bodysizelimit with statusCode: 413.

The browser saw something else. The network tab showed the POST as 500, and the console showed Uncaught Error: Minified React error #441, which React's decoder explains as an error in the Server Components render whose message is hidden in production. The action never ran, its state stayed empty, and the page did not change. A visitor would think the button does nothing and probably try again.

Minified React error #441: the real message is in the server log

React's error decoder gives #441 as: “An error occurred in the Server Components render. The specific message is omitted in production builds to avoid leaking sensitive details. A digest property is included on this error instance which may provide additional details about the nature of the error.” The number only tells you that the server failed while rendering a Server Component or running a Server Action. Production builds keep the reason away from the browser.

To find the reason, read the server's output, not the browser console. In our test that was the next start terminal, which printed Error: Body exceeded 1 MB limit for the same request that the browser logged as #441. On a host, it is the function or runtime log. The Next.js docs say the error's digest is a hash you can match against the server-side logs, which helps when many requests fail at once. In development the original message is passed to the browser, so next dev is often the quickest way to read it.

Raise the limit

The setting lives in next.config. With bodySizeLimit: "5mb" and a rebuild, the same 2 MB upload reached the action and returned its size. Pick a limit just above the largest file you accept; the setting applies to every Server Action in the app.

// next.config.mjs
export default {
  experimental: {
    serverActions: { bodySizeLimit: "5mb" },
  },
};

Tell the visitor before the request

Because the failure was silent on our test, check the size in the browser too. Read input.files[0].size on change, and show “Files up to 4 MB” before the form is sent. The server limit stays as the real guard, since a browser check is easy to skip.

A route handler did not hit this limit: on next start our /api/contact route read the same 2 MB file without complaint. On Vercel, though, the platform's docs set a request body limit for functions of 4.5 MB, and a larger request gets 413 FUNCTION_PAYLOAD_TOO_LARGE before your code runs. For large files, upload straight to storage and send only the link with the form. More Next.js form errors are in our Next.js contact form guide.

Sending attachments without a Server Action

A form that posts straight to Formgong at https://formgong.com/submit never passes through your Server Action, so this Next.js limit does not apply to it. Formgong has its own attachment rules, described in the file upload guide.