Variables defined in `.env` files that do not begin with `NEXT_PUBLIC_` are not available in Middleware deployed to Vercel about next.js HOT 2 OPEN

Generally, when you load environment variables from .env* files, all the Non-NEXT-PUBLIC variables are only available in the Node.js runtime and not in the Edge runtime. This remains true when deployed on vercel too.
However when you configure variables through Vercel's project settings, all environment variables are made available to the edge runtime regardless of their prefix. This explains the inconsistency that you have been experiencing.

Good to know: When deploying your Next.js application to Vercel
, your environment variables in .env* files will not be made available to Edge Runtime, unless their name are prefixed with NEXT_PUBLIC_. We strongly recommend managing your environment variables in Project Settings
instead, from where all environment variables are available.

You can refer to these links to the NextJS documentation:

• Environment variables on vercel.
• Middleware runtime support.
• Edge and Node.js runtimes.

from next.js.

Ok, but why?

It doesn't make sense as it is now. You can't make the case that it is about security, because then it would also apply to non-NEXT_PUBLIC variables defined inside Vercel as well.

It is an inconsistency that makes it impossible to set new environment variables that depend on the VERCEL_ system environment variables, such as MY_ENV="https://${VERCEL_URL}"

It isn't always possible to do this in code--some libs only read environment variables (which is also a poor choice, but not the point here).

from next.js.