Vue-cli 3 Environment Variables all undefined

A few tips for people who land here:

1. Make sure your .env files are in the project root folder (and not in say src/)
2. Variable names should start with VUE_APP_ if to be statically embedded into the client bundle
3. Restart the dev server or build your project for changes to take effect
4. If you are migrating from a webpack based solution make sure that you replace : (from JSON config) with = (dotenv format). Easy to miss
5. Make sure you’ve saved any changes to your .env files.
6. In old Vue versions environment variables were defined in e.g. config/dev.env.js instead of the .env files in root