.env.development File

PORT=3000 LOG_LEVEL=info You, as a developer, need to test on port 8080 with verbose logs. Instead of modifying the committed file (causing merge conflicts), you create .env.local :

| File | Purpose | Git status | | :--- | :--- | :--- | | .env.development | Default dev config for the entire team. Safe, non-sensitive defaults. | ✅ | | .env.local | Local overrides. Your personal API key, different ports, etc. | ❌ Gitignore | Real-world workflow: The team keeps a .env.development file with:

npm install dotenv Create config.js :

Enter the unsung hero of modern software development: . This file, along with its siblings ( .env.production , .env.test ), is the cornerstone of the Twelve-Factor App methodology. It separates code from configuration, ensuring your application runs flawlessly whether it’s on a laptop, a staging server, or a Kubernetes cluster.

Run your app:

REACT_APP_API_BASE_URL=http://localhost:5000 REACT_APP_ENABLE_MOCKING=true SKIP_PREFLIGHT_CHECK=true Next.js loads .env.development automatically during next dev . Variables are inlined at build time. To expose to the browser, prefix with NEXT_PUBLIC_ .

This couples your environment logic to your source code. With .env.development , the code simply reads process.env.API_URL —the file decides the value. The implementation varies slightly, but the philosophy is identical. Node.js + dotenv (Vanilla) Install dotenv : .env.development

NEXT_PUBLIC_GA_TRACKING_ID=UA-DEV-123456 DATABASE_URL=postgresql://user:pass@localhost:5432/dev_db NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY=pk_test_... Use python-dotenv or django-environ .