Environment: server
import type { BuildOptions } from 'esbuild'
type Server =
  | string
  | {
      entry: string | { index: string; [name: string]: string }
      standalone?: boolean | { esbuild: BuildOptions }
      hmr?: boolean | 'prefer-restart'
    }

Local
Provided by: vike-server

You need vike-server to be able to use the +server setting.

The documentation for the various +server settings lives at vike-server.