vercel/next.js · error · Error

The 'public' directory is reserved in Next.js and can not be

Error message

The 'public' directory is reserved in Next.js and can not be set as the 'distDir'. https://nextjs.org/docs/messages/can-not-output-to-public

What it means

Next.js reserves the `public/` directory for serving static files at the site root, so it cannot also be used as `distDir` (the build output directory). Setting `distDir: 'public'` would cause the build to overwrite your static assets. The check is a hard guard in config normalization: any trimmed distDir value equal to 'public' is rejected.

Source

Thrown at packages/next/src/server/config.ts:354

    (currentConfig, key) => {
      const value = (userConfig as any)[key]

      if (value === undefined || value === null) {
        return currentConfig
      }

      if (key === 'distDir') {
        if (typeof value !== 'string') {
          throw new Error(
            `Specified distDir is not a string, found type "${typeof value}"`
          )
        }
        const userDistDir = value.trim()

        // don't allow public as the distDir as this is a reserved folder for
        // public files
        if (userDistDir === 'public') {
          throw new Error(
            `The 'public' directory is reserved in Next.js and can not be set as the 'distDir'. https://nextjs.org/docs/messages/can-not-output-to-public`
          )
        }
        // make sure distDir isn't an empty string as it can result in the provided
        // directory being deleted in development mode
        if (userDistDir.length === 0) {
          throw new Error(
            `Invalid distDir provided, distDir can not be an empty string. Please remove this config or set it to undefined`
          )
        }
      }

      if (key === 'pageExtensions') {
        if (!Array.isArray(value)) {
          throw new Error(
            `Specified pageExtensions is not an array of strings, found "${value}". Please update this config or remove it.`
          )
        }

View on GitHub (pinned to 0ae8c72462)

Solutions

1. Change distDir to a non-reserved directory name such as '.next' (default) or 'build' or '.output'
2. If you need static output, use `output: 'export'` instead of pointing distDir at public

Example fix

// before
module.exports = { distDir: 'public' }
// after
module.exports = { distDir: '.next' }

if (path.basename(distDir.trim()) === 'public') {
  throw new Error('distDir cannot be "public"')
}
const config = { distDir }

const isSafeDistDir = (v: unknown): v is string =>
  typeof v === 'string' && v.trim().length > 0 && v.trim() !== 'public'

When it happens

Trigger: Setting `distDir: 'public'` (or with surrounding whitespace like `' public '`) in next.config.js/ts/mjs. Triggered during loadConfig's reduce step over user config keys.

Common situations: Developer wants build output in a known web-served folder and naively picks 'public'. Copy-pasting a config snippet that named the dir 'public'. Migrating from another framework where output went to a public folder.

Related errors

• Invalid distDir provided, distDir can not be an empty string
• `forbidden()` is experimental and only allowed to be enabled
• `unauthorized()` is experimental and only allowed to be used
• NEXT_EXPORT_ERROR
• Failed to resolve pattern "${patterns.join(',')}": ${error.m

AI-assisted analysis of vercel/next.js@0ae8c72462 (2026-08-06). Data as JSON: /api/errors/ef85356e729ba681. Report an issue: GitHub.