Environment Variable Management Best Practices
Environment variables separate configuration from code, enabling the same application to run in development, staging, and production. Learn secure patterns for managing them.
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The Twelve-Factor Approach
The Twelve-Factor App methodology stores configuration in environment variables. This separates secrets and deployment-specific settings from code, preventing accidental commits of API keys and enabling the same codebase to run across environments.
.env Files for Local Development
Use a .env file for local development, loaded by your application framework. Include .env in .gitignore to prevent secrets from reaching version control. Provide a .env.example with placeholder values documenting all required variables.
Required vs Optional Variables
Validate all required environment variables at application startup. Fail fast with a clear error message listing missing variables rather than crashing deep in business logic when a variable is first accessed. For optional variables, define sensible defaults in code.
Secret Management in Production
Never store secrets in environment variables on disk (.bashrc, docker-compose.yml). Use a secrets manager — AWS Secrets Manager, HashiCorp Vault, 1Password, or your platform's native secrets store. Inject secrets at runtime, not build time. Rotate secrets regularly and audit access.
Naming Conventions
Use SCREAMING_SNAKE_CASE for environment variables. Prefix with your application name to avoid conflicts: MYAPP_DATABASE_URL. Group related variables: MYAPP_SMTP_HOST, MYAPP_SMTP_PORT, MYAPP_SMTP_USER. Use _URL suffixes for connection strings that combine host, port, credentials, and database name.
Common Pitfalls
Don't use environment variables for complex structured data — they're strings, not JSON objects. Don't share the same secrets across environments. Don't log environment variables at startup (leaks secrets). Don't use environment variables for feature flags — use a dedicated feature flag service instead.
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