zCL

Zigbee Cluster Library (ZCL) is a core component of the Zigbee application layer that defines a collection of clusters—functional building blocks representing device capabilities such as lighting, sensing, and security. Each cluster specifies a set of attributes (state data) and commands (actions) that devices can implement and exchange over Zigbee. Clusters are grouped into profiles (for example, Home Automation, Lighting, and Smart Energy), enabling interoperable device behavior across manufacturers.

In ZCL, a device exposes clusters in two roles: server and client. Servers host attributes and respond to commands; clients invoke commands and read or write attributes. Communication within a cluster follows a standard command/response or report mechanism; devices can support periodic attribute reporting to keep peers informed. Attributes have types defined in the ZCL data type specification.

Clusters can be standard (publicly defined by the Zigbee Alliance) or manufacturer-specific. A standard cluster such as On/Off, Level Control, Identify, or Illuminance Measurement enables common functionality across devices. The library provides the structure for definitions, including cluster IDs, attribute IDs, data types, and command sets, and supports commands in both directions.

ZCL is designed to enable interoperability in Zigbee networks, allowing devices from different vendors to control and monitor each other through a consistent API. It remains a foundational element of Zigbee 3.x device implementations and is periodically updated as new functionality is added.