Explain .env code

What this .env sample shows

names and values

Each line is NAME=value, and the app reads it as an environment variable: process.env["PORT"] in Node, os.environ["PORT"] in Python. Lines starting with # are comments, and blank lines are skipped.

quotes and comments

A # after a value starts a comment, so DEBUG=true # this part is a comment came through as true. Inside double quotes it doesn't: WELCOME_TEXT kept Hello # this is part of the value, and the quotes around MAIL_FROM kept its spaces and <team@example.com> in one value.

text only

Every value arrives as a string. In Node, process.env["PORT"] + 1 printed 30001, not 3001, and process.env["DEBUG"] === true was false while === "true" was true. Numbers and true/false have to be converted in your code.

loading the file

Nothing reads a .env file on its own: plain node show.js saw every value as undefined. node --env-file=.env show.js loaded it, and in Python load_dotenv() from python-dotenv does. A variable already set wins: with PORT=8080 set, both kept 8080, and only load_dotenv(override=True) let the file's 3000 win.

Good to know

• This box sends what you paste to Unvibe and Anthropic, and only common key formats are refused, so paste your .env.example or swap each real value for a placeholder first.
• Run with Node 25.7.0 (--env-file) and python-dotenv 1.2.4 on this file: both read the same values, apart from APP_URL (see below).
• A missing file stops Node before your code runs: node --env-file=.env.missing printed node: .env.missing: not found and exited with code 9. --env-file-if-exists printed .env.missing not found. Continuing without it. and ran.
• Keep the real .env out of git and commit a .env.example with the same names and placeholder values, so others know which settings to fill in.

Watch out: ${PORT} isn't filled in everywhere. python-dotenv turned APP_URL into http://localhost:3000, but Node's --env-file passed it through as the text http://localhost:${PORT}, so the same file gave the two apps different URLs. Write the full value out when more than one tool reads the file.