UPDATE - This video uses the version 8.0.2 of env-cmd. In newer versions you have to add the -e flag to make this configuration work. (example:In your package.json, env-cmd -e development react-scripts start) Hi, In this video you will learn how to add environment variables to your React project under different environments such as development, QA and production. If you have any questions, let me know in the comments below :) Required node modules env-cmd - https://www.npmjs.com/package/env-cmd