YAML

Home Assistant uses the YAML syntax for configuration. YAML might take a while to get used to but is really powerful in allowing you to express complex configurations.

While more and more integrations are configured through the UI, for some, you will add code in your configuration.yaml file to specify its settings.

The following example entry assumes that you would like to set up the notify integration with the pushbullet platform.

notify:
  platform: pushbullet
  api_key: "o.1234abcd"
  name: pushbullet

• An integration provides the core logic for some functionality (like notify provides sending notifications).
• A platform makes the connection to a specific software or hardware platform (like pushbullet works with the service from pushbullet.com).

The basics of YAML syntax are block collections and mappings containing key-value pairs. Each item in a collection starts with a - while mappings have the format key: value. This is somewhat similar to a Hash table or more specifically a dictionary in Python. These can be nested as well. Beware that if you specify duplicate keys, the last value for a key is used.

Note that indentation is an important part of specifying relationships using YAML. Things that are indented are nested “inside” things that are one level higher. So in the above example, platform: pushbullet is a property of (nested inside) the notify integration.

Getting the right indentation can be tricky if you’re not using an editor with a fixed width font. Tabs are not allowed to be used for indentation. Convention is to use 2 spaces for each level of indentation.

You can use the online service YAML Validator to check if your YAML syntax is correct before loading it into Home Assistant which will save you some time. If you do so, be aware that this is a third-party service and is not maintained by the Home Assistant community.

Strings of text following a # are comments and are ignored by the system.

The next example shows an input_select integration that uses a block collection for the values of options. The other properties (like name:) are specified using mappings. Note that the second line just has threat: with no value on the same line. Here threat is the name of the input_select and the values for it are everything nested below it.

input_select:
  threat:
    name: "Threat level"
    # A collection is used for options
    options:
      - 0
      - 1
      - 2
      - 3
    initial: 0

The following example shows nesting a collection of mappings in a mapping. In Home Assistant, this would create two sensors that each use the MQTT platform but have different values for their state_topic (one of the properties used for MQTT sensors).

sensor:
  - platform: mqtt
    state_topic: "sensor/topic"
  - platform: mqtt
    state_topic: "sensor2/topic"

Including values

Environment variables

On Home Assistant Core installations, you can include values from your system’s environment variables with !env_var. Note that this will only work for Home Assistant Core installations, in a scenario where it is possible to specify these. Regular Home Assistant users are recommended to use !include statements instead.

example:
  password: !env_var PASSWORD

Default value

If an environment variable is not set, you can fallback to a default value.

example:
  password: !env_var PASSWORD default_password

Including entire files

To improve readability, you can source out certain domains from your main configuration file with the !include-syntax.

light: !include lights.yaml

More information about this feature can also be found at splitting configuration.

Common Issues

found character ‘\t’

If you see the following message:

found character '\t' that cannot start any token

This means that you’ve mistakenly entered a tab character, instead of spaces.

Upper and lower case

Home Assistant is case sensitive, a state of 'on' is not the same as 'On' or 'ON'. Similarly an entity of group.Doors is not the same as group.doors.

If you’re having trouble, check the case that Home Assistant is reporting in the dev-state menu, under Developer tools.

Booleans

YAML treats Y, true, Yes, ON all as true and n, FALSE, No, off as false. This means that if you want to set the state of an entity to on you must quote it as 'on' otherwise it will be translated as setting the state to true. The same applies to off.

Not quoting the value may generate an error such as:

not a valid value for dictionary value @ data