Introduction

• Text file that stores env vars (vars provided to app by OS / runtime).
• Key=value pairs.
• Used to store config + secrets

It help to make

• Secrets stay outside code (no leak)
  • Put in gitignore
• Different values for:
  • local
  • staging
  • production
• Same code, different behavior

How it works

Node.js / Frontend (Vite, Next.js)

They use a library like dotenv

1. Read .env
2. Put values into process.env
3. Your app access the env var

Docker & Docker Compose

1. Reads .env
2. Injects variables into the container