Accessing Env Vars In create-react-app

Environment-specific configurations are an important part of most applications. You can access environment variables in your create-react-app code using process.env.

There are a couple built-in environment variables, such as NODE_ENV. Anything custom that you want to provide must be prepended with REACT_APP_. If it isn't, that environment variable will be ignored with no warning.

The following line of code

const base_api_url = process.env.REACT_APP_BASE_API_URL;

will have access to whatever that value is in the environment when the server is started or the app is built.

Set that value inline like so:

REACT_APP_BASE_API_URL="https://api.my_app.com" yarn start

source