home-assistant.io/source/_includes/integrations/using_templates.md

Using templates

For incoming data, a value template translates incoming JSON or raw data to a valid payload. Incoming payloads are rendered with possible JSON values, so when rendering, the value_json can be used to access the attributes in a JSON based payload, otherwise the value variable can be used for non-json based data.

Additional, the this can be used as variables in the template. The this attribute refers to the current entity state of the entity. Further information about this variable can be found in the template documentation

{% note %}

Example value template with json:

With given payload:

{ "state": "ON", "temperature": 21.902 }

Template {% raw %}{{ value_json.temperature | round(1) }}{% endraw %} renders to 21.9.

{% endnote %}