Env Vars Cheatsheet - .env Config & dotenv Usage

Almost every Node/Python/frontend project writes a .env, yet the most common traps are spaces around the equals sign, a # inside a value treated as a comment, and secrets accidentally committed to the repo. This reference covers 5 groups: variable definition, reading in Shell/Node/Python, dotenv loader usage, multi-environment file layout (.env/.env.local/.env.production), and a set of security-pitfall reminders. Sanity-check the format after writing and confirm no secrets were committed before deploying. After reading you can organize environment variables cleanly and avoid the most common leakage issues.

Config Formats·24 commands·Last updated 2026-08-02

Definition 6

KEY=value

Define a variable (no spaces around =)

KEY="value with space"

Quote values with spaces or special chars

KEY='literal $NOT_EXPANDED'

Single quotes: no variable expansion

KEY=${OTHER}_suffix

Double quotes: reference other variables

# comment

Hash starts a comment line

export KEY=value

Set and export as an environment variable

Reading 5

echo $KEY

Read in shell (Linux/macOS)

echo %KEY%

Read in Windows cmd

$env:KEY

Read in PowerShell

process.env.KEY

Read in Node.js

os.getenv("KEY")

Read in Python

dotenv Usage 4

require('dotenv').config()

Node: load .env into process.env

import 'dotenv/config'

ESM import to load .env

dotenv.config({ path: '.env.local' })

Load with a custom file path

python-dotenv load_dotenv()

Python: load .env

Multi-environment Files 5

.env

Default env (don't commit to git)

.env.local

Local override (higher priority)

.env.development

Development env

.env.production

Production env

.env.example

Example template, committable, no real secrets

Security FAQ 4

Don't commit secrets

Don't commit secrets

Case sensitive

Case sensitive

Type conversion

Type conversion

Escape newlines

Escape newlines

Tips

No spaces around = (KEY=value is correct, KEY = value is wrong).
Add .env to .gitignore; commit secrets via .env.example template instead.
All values are strings; convert numbers with Number()/parseInt().
Multi-line values use quotes or \n for newlines.

Official References

Each command links to its official documentation below, so you can verify the latest usage and read deeper.

dotenv

Maintained by LaoHand

Publicly updated on Aug 2, 2026, continuously proofread against official docs.

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