.env files

What are Environment Files?

Environment files (commonly named .env) are configuration files that store environment variables for your application. They contain sensitive information and configuration settings that may vary between different environments (development, staging, production).

Purpose

Environment files serve several important purposes:

• Security: Keep sensitive data (API keys, passwords, tokens) out of your source code
• Configuration: Store environment-specific settings that change between development and production
• Flexibility: Allow different team members to use their own configurations without conflicts
• Separation of concerns: Keep configuration separate from application logic

Common data stored in .env files includes:

• Database connection strings
• API keys and secrets
• Third-party service credentials
• Environment-specific URLs
• Feature flags
• Port numbers

File Structure

Environment files follow a simple key-value pair structure. Each line contains one variable in the format KEY=value.

Basic Syntax

# This is a comment
DATABASE_URL=postgresql://user:password@localhost:5432/mydb
API_KEY=abc123xyz789
PORT=3000
NODE_ENV=development

Naming Conventions

• Use UPPERCASE for variable names
• Separate words with underscores (snake_case)
• Be descriptive but concise
• Group related variables with common prefixes

# Database configuration
DB_HOST=localhost
DB_PORT=5432
DB_NAME=myapp
DB_USER=admin
DB_PASSWORD=secret123

# API configuration
API_BASE_URL=https://api.example.com
API_KEY=your_api_key_here
API_TIMEOUT=5000

Value Types

# Strings (no quotes needed, but can use them)
APP_NAME=My Application
APP_DESCRIPTION="An awesome app"

# Numbers
PORT=3000
MAX_CONNECTIONS=100

# Booleans (stored as strings)
DEBUG=true
ENABLE_LOGGING=false

# URLs
DATABASE_URL=postgresql://localhost/mydb

# Empty values
OPTIONAL_KEY=

# Multiline values (use quotes)
PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----
MIIEpAIBAAKCAQEA...
-----END RSA PRIVATE KEY-----"

Git and Version Control

Never Track .env Files

Important: .env files should NOT be tracked by Git because they contain sensitive information.

Add .env to your .gitignore file:

.gitignore

.env
.env.local
.env.*.local

What to Track Instead

Create an .env.example or .env.template file that shows the structure without sensitive values:

.env.example

DATABASE_URL=postgresql://user:password@host:port/database
API_KEY=your_api_key_here
PORT=3000
NODE_ENV=development

This file should be tracked in Git because it:

• Documents required environment variables
• Helps new developers set up their environment
• Shows the structure without exposing secrets

Deployment settings

If you are deploying your application to a hosting platform like Combell, you need to set the environment variables there as well. Of course this will differ from your local .env file. So make sure you don’t just upload your local .env file to the server.

Other hosting platforms like GitHub Pages, Vercel, Netlify, Heroku, etc. provide dashboards to set environment variables directly. You typically do this in the project settings and do not upload .env files.

Loading Environment Variables

Node.js with dotenv

npm install dotenv

// At the top of your main file
require('dotenv').config();

// Or with ES modules
import 'dotenv/config';

// Access variables
const dbUrl = process.env.DATABASE_URL;
const apiKey = process.env.API_KEY;

Vite

Vite has built-in support for .env files. Only variables prefixed with VITE_ are exposed to client-side code:

.env

VITE_API_URL=https://api.example.com
VITE_APP_TITLE=My App
DATABASE_URL=postgresql://...  # Not exposed to client

// In your Vite app
const apiUrl = import.meta.env.VITE_API_URL;