`process.env` is undefined in local production build even with dotenv-cli installed and accessing env server-only

[nikolailehbrink]

I'm using React Router as a...

framework

Reproduction

https://stackblitz.com/edit/github-qphddjff?file=app%2Froutes%2Fhome.tsx

1. Open the repro
2. Clear the terminal and build it locally with npm run build
3. Start the preview server with npm run start
4. See that it logs undefinedin the loader, although I even installed dotenv-cli which according to this discussion should fix it
5. When uncommenting the define in vite-config.ts it works, however I get a warning while building, that this could be a security flaw

System Info

System:
    OS: macOS 15.5
    CPU: (10) arm64 Apple M1 Max
    Memory: 222.20 MB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.13.0 - ~/.nvm/versions/node/v22.13.0/bin/node
    Yarn: 1.22.22 - ~/.nvm/versions/node/v22.13.0/bin/yarn
    npm: 10.9.2 - ~/.nvm/versions/node/v22.13.0/bin/npm
    pnpm: 10.12.1 - ~/.nvm/versions/node/v22.13.0/bin/pnpm
    bun: 1.1.45 - ~/.nvm/versions/node/v22.13.0/bin/bun
  Browsers:
    Chrome: 137.0.7151.105
    Safari: 18.5
  npmPackages:
    @react-router/dev: ^7.5.3 => 7.6.2 
    @react-router/node: ^7.5.3 => 7.6.2 
    @react-router/serve: ^7.5.3 => 7.6.2 
    react-router: ^7.5.3 => 7.6.2 
    vite: ^6.3.3 => 6.3.5

Used Package Manager

npm

Expected Behavior

When starting the production build locally, all environment variables from .env should be available in server-side loader functions.

Actual Behavior

I’m running into the same issue as described in this discussion, but even with dotenv-cli installed and the recommended setup, environment variables are not available during a local production build.

[timdorr]

If you run with an environment variable set on the command line, it will work: test=foo npm start I believe you are misunderstanding how environment variables (ENVs) work and how the dotenv-cli package works as well. It is best to set them via system tools, such as those provided by your hosting provider or a tool like Docker or Kubernetes. If you just want to see your production build running locally and use the .env file you have locally (make sure you're not committing it to source control and include it in your .gitignore file!), you would install dotenv-cli globally and use as the instructions describe: https://github.com/entropitor/dotenv-cli#installing

Also, and this is unrelated, but as a matter of convention ENVs are usually capitalized.

[nikolailehbrink]

Hi @timdorr, thanks for the answer!
I installed the dotenv-cli package in the stackblitz repro because there was no way to show, that I have the package installed globally on my device and it still didn't work for me. I took another look at dotenv and you're right, I misunderstood the ENV's a little bit. Fixed it now by calling dotenv inside the start script (e.g.: "start": "dotenv react-router-serve ./build/server/index.js",, instead of the build script.