vercel/next.js · error · Error

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

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

Config validation in assignDefaultsAndValidate: the distDir string, after trimming, equals 'public'. The public directory is reserved for static assets served from the site root — using it as the build output directory would collide with user files, so the value is rejected outright.

Solutions

1. Choose a different distDir; 'public' is reserved.

When it happens

Trigger: distDir is set to the reserved public directory.

Common situations: Configuring distDir: 'public' in next.config, which conflicts with Next.js static serving.

AI-assisted analysis of vercel/next.js@34433fd12e (2026-08-19). Data as JSON: /api/errors/ef85356e729ba681. Report an issue: GitHub.

Appendix: source

Thrown at packages/next/src/server/config.ts:389

    (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.`
          )
        }

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