Docker Compose YAML to JSON Conversion

Docker Compose files are one of the most common real-world uses of YAML in software development. Understanding their JSON equivalent helps when working with Docker APIs or generating configurations programmatically.

A typical docker-compose.yml:

version: "3.8"

services:
  web:
    build: ./app
    ports:
      - "3000:3000"
    environment:
      - NODE_ENV=production
      - DATABASE_URL=postgres://db:5432/myapp
    depends_on:
      - db
      - redis
    volumes:
      - ./app:/usr/src/app
      - node_modules:/usr/src/app/node_modules

  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_DB: myapp
      POSTGRES_PASSWORD: secret
    volumes:
      - pgdata:/var/lib/postgresql/data

  redis:
    image: redis:7-alpine
    ports:
      - "6379:6379"

volumes:
  pgdata:
  node_modules:

The JSON equivalent:

{
  "version": "3.8",
  "services": {
    "web": {
      "build": "./app",
      "ports": ["3000:3000"],
      "environment": [
        "NODE_ENV=production",
        "DATABASE_URL=postgres://db:5432/myapp"
      ],
      "depends_on": ["db", "redis"],
      "volumes": [
        "./app:/usr/src/app",
        "node_modules:/usr/src/app/node_modules"
      ]
    },
    "db": {
      "image": "postgres:16-alpine",
      "environment": {
        "POSTGRES_DB": "myapp",
        "POSTGRES_PASSWORD": "secret"
      },
      "volumes": ["pgdata:/var/lib/postgresql/data"]
    },
    "redis": {
      "image": "redis:7-alpine",
      "ports": ["6379:6379"]
    }
  },
  "volumes": {
    "pgdata": null,
    "node_modules": null
  }
}

Notable conversion details:

• Environment variables can be either an array of strings (- KEY=value) or an object (KEY: value). Both are valid in Docker Compose.
• Empty volume definitions (pgdata: with no value) become null in JSON.
• Port mappings should be quoted in YAML ("3000:3000") to prevent the colon from being interpreted as a nested key.