How to fix services.myservice Additional property X is not allowed in Docker

The error message tells you exactly which property is problematic. Read it carefully:

services.web Additional property enviroment is not allowed

In this example:
- Location: services.web - the problem is in the "web" service
- Property: enviroment - this is the unrecognized property (note the typo!)

Common typos to look for:
| Wrong | Correct |
|-------|---------|
| enviroment | environment |
| sevices | services |
| service | services |
| env_files | env_file |
| port | ports |
| volume | volumes |
| depens_on | depends_on |
| bulid | build |

In Compose file version 2 and later, all service definitions must be nested under a services: key. This is the most common cause of this error for beginners.

Wrong - services at root level:

version: "3"
web:
  image: nginx
  ports:
    - "80:80"

Correct - services under 'services:' key:

version: "3"
services:
  web:
    image: nginx
    ports:
      - "80:80"

If you see an error like (root) Additional property web is not allowed, this is almost certainly the cause.

YAML requires consistent indentation with spaces (not tabs). Incorrect indentation can make properties appear at the wrong level.

Wrong - deploy appears as a separate service:

services:
  web:
    image: nginx
  deploy:              # Wrong! This looks like a service named "deploy"
    replicas: 3

Correct - deploy is a property of web:

services:
  web:
    image: nginx
    deploy:            # Correct! Indented under web
      replicas: 3

Use a YAML validator or your editor's YAML support to check indentation. Most editors can visualize indentation levels.

To check for tabs vs spaces:

# Show tabs as ^I
cat -A docker-compose.yml

# Or use grep to find tabs
grep -P '\t' docker-compose.yml

If you find tabs, replace them with spaces (typically 2 spaces per level):

# Replace tabs with 2 spaces
sed -i 's/\t/  /g' docker-compose.yml

Use Docker Compose's built-in validation to check your file:

# Using Docker Compose V2 (recommended)
docker compose config

# Using legacy docker-compose
docker-compose config

This command parses and validates your file, showing exactly where problems occur. If the file is valid, it outputs the processed configuration.

You can also use online validators:
- [Docker Compose Validator](https://yamlchecker.com/) - General YAML validation
- Your IDE's built-in YAML/Docker Compose support

For a quick syntax check without running Docker:

# Check YAML syntax with Python
python3 -c "import yaml; yaml.safe_load(open('docker-compose.yml'))"

Some properties are only available in newer Docker Compose versions. Check your version:

docker compose version
# or
docker-compose --version

Common properties and their minimum version requirements:

| Property | Minimum Version |
|----------|-----------------|
| include | Docker Compose 2.20.0 |
| configs.*.content | Docker Compose 2.23.0 |
| deploy.replicas | Compose file version 3.0+ |
| healthcheck | Compose file version 2.1+ |
| platform | Docker Compose 2.4.0 |

If you're using a feature not supported by your version, either:
1. Upgrade Docker Compose: sudo apt-get update && sudo apt-get install docker-compose-plugin
2. Remove the unsupported property from your file
3. Use an alternative approach compatible with your version

Docker Compose only allows specific top-level keys. Using anything else triggers this error.

Valid top-level keys:

version: "3.8"          # Optional in Compose V2
name: my-project        # Project name (optional)
services:               # Service definitions (required)
networks:               # Network definitions (optional)
volumes:                # Volume definitions (optional)
configs:                # Config definitions (optional)
secrets:                # Secret definitions (optional)
x-*:                    # Extension fields (optional)
include:                # Include other files (Compose 2.20+)

Invalid example:

version: "3"
myservice:              # Wrong! Should be under 'services:'
  image: nginx

The error (root) Additional property myservice is not allowed means you're defining something at the root level that isn't one of the valid top-level keys.

Each service has a specific set of allowed properties. Common misplacements include:

Wrong - environment under build:

services:
  web:
    build:
      context: .
      environment:     # Wrong! environment goes under service, not build
        - NODE_ENV=prod

Correct - environment under service:

services:
  web:
    build:
      context: .
    environment:       # Correct! At service level
      - NODE_ENV=prod

Common service-level properties:
- image, build, command, entrypoint
- environment, env_file
- ports, expose
- volumes, networks
- depends_on, links
- deploy, healthcheck
- restart, container_name

When in doubt, consult the [Compose Specification](https://docs.docker.com/compose/compose-file/) for the complete list.