# Using environment variables in React applications In React applications (e.g. those using `@nrwl/web:webpack` or `@nrwl/next:build` executors for `build` target), Nx includes the following variables in the build process: - `NODE_ENV` - Variables prefixed with `NX_`, such as `NX_CUSTOM_VAR` Defining environment variables can vary between OSes. It's also important to know that this is temporary for the life of the shell session. ## Using environment variables in `index.html` Nx supports interpolating environment variables into your `index.html` file for React and Web applications. To interpolate an environment variable named `NX_DOMAIN_NAME` into your `index.html`, surround it with `%` symbols like so: ```html {% fileName="index.html" %}

The domain name is %NX_DOMAIN_NAME%.

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