Are .env file variables included in the build package?

It seems like they are, even though they’re in the project’s .gitignore. If I do a netliify dev or deploy, process.env.MY_ENV_FILE_VARIABLE appears to be pulled into the deploy environment, where it is accessible by client code running on a browser. Not what I want.

I want MY_ENV_FILE_VARIABLE not to be accessible from a deployed build. Do I have to use dotenv, for instance?

When running netlify deploy, the project is built locally and deployed to Netlify. Thus those environment variables are injected during the build process—this isn’t Netlify doing this, rather the build tool used such as React or Vue.