TOOLADEX

.env File Validator

Validate your .env configuration files for syntax errors, security issues, and best practice violations. All validation happens locally in your browser — your sensitive data never leaves your device.

100% Client-Side Processing

Your .env contents are validated entirely in your browser. No data is sent to any server.

What We Check

🔴 Errors

  • • Missing equals sign
  • • Invalid key names
  • • Duplicate keys
  • • Mismatched quotes
  • • Unclosed interpolation

🟡 Warnings

  • • Empty values
  • • Unquoted spaces
  • • Trailing whitespace
  • • Placeholder secrets
  • • URL with credentials

🔵 Info

  • • Lowercase key names
  • • Commented variables
  • • Sensitive data detection

✅ Auto-Fix

  • • Uppercase key names
  • • Remove extra whitespace
  • • Quote values with spaces
  • • Comment out invalid lines

Table of Contents

What is an .env File?

An .env file (short for "environment") is a simple text file used to store environment variables for your application. It provides a convenient way to manage configuration settings that may vary between development, staging, and production environments.

Environment variables stored in .env files typically include database credentials, API keys, feature flags, and other configuration that shouldn't be hardcoded in your application's source code. This separation of configuration from code is a key principle of the Twelve-Factor App methodology.

Popular libraries like dotenv (Node.js, Python, Ruby) automatically load these variables into your application's environment at runtime.

.env File Syntax

The syntax of a .env file is straightforward, but there are some nuances to be aware of:

# This is a comment
DATABASE_URL=postgres://localhost/mydb
API_KEY=abc123

# Values with spaces need quotes
APP_NAME="My Application"

# Or use single quotes
MESSAGE='Hello, World!'

# Variable interpolation (some libraries support this)
BASE_URL=https://api.example.com
API_ENDPOINT=${BASE_URL}/v1

Key Rules

  • No spaces around =: KEY=value not KEY = value
  • Comments start with #: Entire line becomes a comment
  • Empty lines are ignored: Use them for organization
  • Quote values with spaces: Use double or single quotes
  • No export keyword: Unlike shell scripts, don't use export

Common Mistakes

❌ Spaces around the equals sign

DATABASE_HOST = localhost

The key becomes "DATABASE_HOST " and value " localhost"

✅ Correct

DATABASE_HOST=localhost

❌ Unquoted values with spaces

APP_NAME=My Cool App

Behavior varies by library — may only get "My" or include spaces literally

✅ Correct

APP_NAME="My Cool App"

❌ Duplicate keys

API_KEY=key1
API_KEY=key2

The second value will override the first, which is usually a mistake

✅ Correct

API_KEY=key1
BACKUP_API_KEY=key2

❌ Placeholder values in production

SECRET_KEY=your_secret_key_here
API_TOKEN=<INSERT_TOKEN>

Placeholder values indicate incomplete configuration

✅ Correct

SECRET_KEY=a1b2c3d4e5f6g7h8i9j0
API_TOKEN=sk-prod-abc123xyz789

Best Practices

Use UPPERCASE_SNAKE_CASE

Environment variable names are conventionally written in uppercase with underscores separating words. This makes them easily distinguishable from regular variables in your code.

Create a .env.example file

Maintain a .env.example file with all required variables (but fake/empty values) that you commit to version control. This documents what variables are needed without exposing secrets.

Group related variables

Use comments and blank lines to organize your .env file into logical sections (database, API keys, feature flags, etc.).

Document complex values

Add comments above variables that have specific format requirements or valid value ranges.

Validate on startup

Use libraries like envalid (Node.js) or pydantic (Python) to validate environment variables when your app starts.

Security Considerations

Never commit .env files to version control! Add .env to your .gitignore file.

Sensitive Data Protection

  • Use a secrets manager (AWS Secrets Manager, HashiCorp Vault) for production
  • Rotate secrets regularly, especially after team member departures
  • Use different credentials for each environment
  • Audit who has access to production environment variables

URL Credentials

Avoid embedding credentials in URLs like postgres://user:password@host/db. These can leak through logs, error messages, and browser history. Use separate variables instead.

Frequently Asked Questions

Is my .env data sent to a server?

No. All validation happens entirely in your browser using JavaScript. Your .env contents never leave your device. This tool is designed with privacy as a top priority, which is why we explicitly avoid any server-side processing or AI analysis.

What's the difference between .env and .env.local?

Different frameworks use different conventions. Generally, .env contains defaults, while .env.local contains machine-specific overrides that shouldn't be committed. Check your framework's documentation for specifics.

Should I quote all values?

Not necessarily. Quoting is only required for values containing spaces, special characters, or newlines. However, some teams prefer to always quote values for consistency. The key is to be consistent within your project.

Does variable interpolation work?

It depends on your library. The standard dotenv library doesn't support it, but dotenv-expand does. Syntax like ${OTHER_VAR} may or may not work depending on your setup.

Can I use multiline values?

Some libraries support multiline values using quotes or backslash continuation. For example: PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----\n...". Check your library's documentation for supported syntax.

Why are lowercase keys flagged?

It's just a convention warning. Environment variables are traditionally UPPERCASE_SNAKE_CASE by Unix convention. While lowercase keys work technically, using uppercase helps distinguish environment variables from regular variables and follows established conventions.