Common mistakes teams make with .env files — and how to avoid them

Common mistakes teams make with .env files — and how to avoid them

Environment files seem simple until they're not. A missing variable brings down production. A typo wastes hours of debugging. An undocumented key confuses new developers for days.

The copy-paste trap

The most common mistake? Copying .env.example, forgetting to replace placeholder values, and deploying your_api_key_here to staging. The app boots successfully because the variable exists, but fails mysteriously when it tries to authenticate. Hours later, someone discovers the placeholder text in production logs.

The fix: Implement startup validation. Use libraries like envalid (Node.js), python-dotenv with validators (Python), or phpdotenv (PHP) to check variables at boot time. Fail fast and loudly if required values are missing or contain obvious placeholders like changeme or xxx. Add CI/CD checks that scan for common placeholder patterns before deployment.

Inconsistent naming chaos

One developer uses DB_HOST, another prefers DATABASE_URL, a third opts for db_connection_string. Different services use different conventions. New team members don't know which is correct. Deployment scripts break because someone assumed the wrong variable name.

The fix: Establish naming conventions in a team document. Use SCREAMING_SNAKE_CASE consistently. Prefix variables by service (REDIS_URL, POSTGRES_HOST, STRIPE_API_KEY). Group related variables together in the file. When adding new variables, grep existing ones first to match established patterns. Consider using a schema validator to enforce naming rules automatically.

Undocumented variables

Six months later, nobody remembers what LEGACY_API_KEY does. Is it still used? Can it be removed? What service needs it? Developers are afraid to delete it, so it lingers forever. New team members spend days deciphering cryptic variable names.

The fix: Treat .env.example as documentation. Add comments above each variable explaining its purpose, expected format, and where to obtain values. Include examples of valid values. Note which variables are optional. Link to relevant documentation or dashboards. When adding new variables, updating .env.example should be mandatory, not optional.

Missing local overrides

Developers share a single .env file or check it into version control. One person's local database credentials overwrite everyone else's. Secrets leak into git history. Local development becomes fragile.

The fix: Use layered configuration. Check in .env.example with placeholders and documentation. Ignore .env and .env.local in git. Let developers create .env.local to override defaults without affecting others. Many frameworks support this pattern natively—use it.

The real fix

Make environment configuration boring. Use validation to fail fast on missing variables. Implement pre-commit hooks that check for placeholders. Document everything in .env.example. Review environment changes during code review like any other code. The goal isn't perfection—it's making mistakes impossible to deploy.