--- description: Compose file reference keywords: fig, composition, compose, docker redirect_from: - /compose/yml - /compose/compose-file-v3.md title: Compose file version 3 reference toc_max: 4 toc_min: 1 --- ## Reference and guidelines These topics describe version 3 of the Compose file format. This is the newest version. ## Compose and Docker compatibility matrix There are several versions of the Compose file format – 1, 2, 2.x, and 3.x. The table below is a quick look. For full details on what each version includes and how to upgrade, see **[About versions and upgrading](compose-versioning.md)**. {% include content/compose-matrix.md %} ## Compose file structure and examples 

version: "3"
services:

redis:
  image: redis:alpine
  ports:
    - "6379"
  networks:
    - frontend
  deploy:
    replicas: 2
    update_config:
      parallelism: 2
      delay: 10s
    restart_policy:
      condition: on-failure
db:
  image: postgres:9.4
  volumes:
    - db-data:/var/lib/postgresql/data
  networks:
    - backend
  deploy:
    placement:
      constraints: [node.role == manager]
vote:
  image: dockersamples/examplevotingapp_vote:before
  ports:
    - 5000:80
  networks:
    - frontend
  depends_on:
    - redis
  deploy:
    replicas: 2
    update_config:
      parallelism: 2
    restart_policy:
      condition: on-failure
result:
  image: dockersamples/examplevotingapp_result:before
  ports:
    - 5001:80
  networks:
    - backend
  depends_on:
    - db
  deploy:
    replicas: 1
    update_config:
      parallelism: 2
      delay: 10s
    restart_policy:
      condition: on-failure

worker:
  image: dockersamples/examplevotingapp_worker
  networks:
    - frontend
    - backend
  deploy:
    mode: replicated
    replicas: 1
    labels: [APP=VOTING]
    restart_policy:
      condition: on-failure
      delay: 10s
      max_attempts: 3
      window: 120s
    placement:
      constraints: [node.role == manager]

visualizer:
  image: dockersamples/visualizer:stable
  ports:
    - "8080:8080"
  stop_grace_period: 1m30s
  volumes:
    - "/var/run/docker.sock:/var/run/docker.sock"
  deploy:
    placement:
      constraints: [node.role == manager]

networks:
  frontend:
  backend:

volumes:
  db-data:
The topics on this reference page are organized alphabetically by top-level key to reflect the structure of the Compose file itself. Top-level keys that define a section in the configuration file such as `build`, `deploy`, `depends_on`, `networks`, and so on, are listed with the options that support them as sub-topics. This maps to the `: