The .env.development.local file is a specialized environment variable file used to store configuration settings and sensitive information (like API keys or database credentials) specifically for a developer's during the development phase . Its primary characteristics include:
: If you are running a local instance of MongoDB or PostgreSQL, you can define your DATABASE_URL here.
: It is strictly for local use and should never be committed to version control (Git). .env.development.local
: Variables here only load when the application is running in "development" mode (e.g., via npm run dev or npm start ). The Hierarchy of .env Files
Tools like Next.js follow a strict load order to determine which variable takes precedence. Generally, the more specific a file is, the higher its priority: : Variables here only load when the application
: Safely enable experimental features on your machine without forcing them on other developers. Best Practices Environment variables - Vercel
(Highest priority for local development) .env.local .env.development .env (Lowest priority; general defaults) general defaults) By using .env.development.local
By using .env.development.local , a developer can test features with their own unique database string or API key without affecting the rest of the team's shared .env.development file. Key Use Cases
: When working with third-party services like OpenAI, you can store your personal OPENAI_API_KEY here so it doesn't leak into the repository.
