vercel/next.js · error

Port ${originalPort} is in use by process ${pid}, using avai

Error message

Port ${originalPort} is in use by process ${pid}, using available port ${port} instead.

What it means

Warning from startServer's listening handler when port retrying was enabled (portRetryCount > 0): the requested originalPort is already bound, so the server fell back to the next available port. It resolves the holding process id via getProcessIdUsingPort and reports which pid holds the original port and which port is actually being used instead.

Source

Thrown at packages/next/src/server/lib/start-server.ts:339

      const addr = server.address()
      const actualHostname = formatHostname(
        typeof addr === 'object'
          ? addr?.address || hostname || 'localhost'
          : addr
      )
      const formattedHostname =
        !hostname || actualHostname === '0.0.0.0'
          ? 'localhost'
          : actualHostname === '[::]'
            ? '[::1]'
            : formatHostname(hostname)

      port = typeof addr === 'object' ? addr?.port || port : port

      if (portRetryCount) {
        const pid = await getProcessIdUsingPort(originalPort)
        if (pid) {
          Log.warn(
            `Port ${originalPort} is in use by process ${pid}, using available port ${port} instead.`
          )
        } else {
          Log.warn(
            `Port ${originalPort} is in use by an unknown process, using available port ${port} instead.`
          )
        }
      }

      const networkHostname =
        hostname ?? getNetworkHost(isIPv6(actualHostname) ? 'IPv6' : 'IPv4')

      const protocol = selfSignedCertificate ? 'https' : 'http'

      const networkUrl = networkHostname
        ? `${protocol}://${formatHostname(networkHostname)}:${port}`
        : null

View on GitHub (pinned to 89d017eac4)

Solutions

1. Stop the process using the port, or accept the automatically selected port.

When it happens

Trigger: Thrown at packages/next/src/server/lib/start-server.ts:339 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of vercel/next.js@89d017eac4 (2026-08-19). Data as JSON: /api/errors/1f26dc19d856d67e. Report an issue: GitHub.