# docker compose: services.x Additional property y is not allowed / yaml: line N: mapping values are not allowed

**Code:** `compose validation` · **Category:** Docker · **Seen on:** Docker

The compose file is invalid YAML or uses a key Compose doesn’t recognise at that level (usually an indentation mistake).

## Meaning

YAML is indentation-sensitive. A key indented one level too far or too little ends up under the wrong parent, producing “Additional property … is not allowed”. Tabs and unquoted colons cause “mapping values are not allowed”.

## Common causes

- Wrong indentation (key under the wrong parent)
- Tabs instead of spaces
- Unquoted values containing `: ` (e.g. command strings)
- Typos in keys (`enviroment`, `port`)
- Old `version:` / v2-only keys with Compose v2

## Quick fix

1. Validate: `docker compose config`
2. Use 2-space indentation, no tabs
3. Quote strings containing colons
4. Check key spelling against the Compose spec

## Detailed fix by platform

### Docker

1. Correct structure:

```yaml
services:
  web:
    image: nginx:1.27
    ports:
      - "8080:80"          # quoted: contains a colon
    environment:
      APP_ENV: production
```


## How to diagnose

1. **Validate** — `docker compose config` output
2. **Line** — Which line/key is reported?
3. **Whitespace** — Tabs or mixed indentation?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/docker/docker-compose-invalid-yaml)