Setting process.env.NODE_ENV is a widespread convention to tell tools whether your app is being run in development or production.

It's important to respect the following convention: many tools run erroneously otherwise.

In development:

• Make sure process.env.NODE_ENV is one of these values: ['development', 'dev', '', undefined].
• If you use a server, make sure to use createDevMiddleware() for adding the development middleware to your server.

In production (and staging):

• Make sure process.env.NODE_ENV is a value different than ['development', 'dev', '', undefined].

  Note that:

  • Upon starting your server in production, make sure to set process.env.NODE_ENV. (E.g. $ NODE_ENV='production' node server/index.js.)
  • Upon building ($ vike build/$ vike prerender), process.env.NODE_ENV is automatically set to 'production'.

• Make sure you don't call createDevMiddleware() in production: the development middleware isn't needed in production. (It would unnecessarily bloat your production server.)
• Make sure you don't mistakenly load Vite in production. (It would significantly bloat your production server.)

See also

• Node.js Docs - The difference between development and production

  While the process.env.NODE_ENV convention was introduced by Node.js, it's used by tools regardless of whether you use Node.js. Thus, make sure to follow the convention even in non-Node.js environments.

• Stack Overflow - What is NODE_ENV and how to use it in Express?