# Domain

> The short, unique identifier of an integration, like `hue` or `light`. It is also the first part of every entity ID.

Source: https://contributors.home-assistant.io/glossary/domain/

- In code: `DOMAIN`, `"domain" in manifest.json`

The domain is the name of the integration's folder, and the `domain` key in its manifest. It is lowercase, with underscores between words, and never changes once an integration is released.

Entities have a domain too: the type of entity, like `light` in `light.kitchen`. That is the domain of the integration that defines the entity type, not of the integration that provides the entity. A Hue lamp is `light.living_room`, not `hue.living_room`.

## Related terms

- [Integration](https://contributors.home-assistant.io/glossary/integration/): A package of code that connects Home Assistant to a device, service, or protocol, or adds a feature like automations.
- [Entity ID](https://contributors.home-assistant.io/glossary/entity-id/): The ID of an entity: its domain and an object ID, like `light.kitchen`.
- [Platform](https://contributors.home-assistant.io/glossary/platform/): How an integration provides one type of entity, like the `light` platform of the Hue integration. Also used for integration platforms, files that plug into another integration.