Home Assistant is free and open-source software used for home automation. It serves as an integration platform and smart home hub, allowing users to control smart home devices. The software emphasizes local control and privacy and is designed to be independent of any specific Internet of Things (IoT) ecosystem. Its interface can be accessed through a web-based user interface, by using companion apps for Android and iOS, or by voice commands via a supported virtual assistant, such as Google Assistant, Amazon Alexa, Apple Siri, and Home Assistant's own "Assist" (a built-in local voice assistant) using natural language.
The Home Assistant software application is commonly run on a computer appliance with "Home Assistant Operating System" that will act as a central control system for home automation (commonly called a smart home hub/gateway/bridge/controller), that has the purpose of controlling IoT connectivity technology devices, software, applications and services from third-parties via modular integration components, including native integration components for common wired or wireless communication protocols and standards for IoT products such as Bluetooth, Zigbee, Z-Wave, EnOcean, and Thread/Matter (used to create either local personal area networks or direct ad hoc connections with small smart home devices using low-power digital radios), or Wi-Fi and Ethernet connected devices on a home network / local area network (LAN).
Home Assistant as such supports controlling devices and services connected via either open and proprietary ecosystems or commercial smart home hubs/gateways/bridges as long they provide public access via some kind of Open API or MQTT interface to allow for third-party integration over either the local area network or Internet, which includes integrations for Alexa Smart Home (Amazon Echo), Google Nest (Google Home), HomeKit (Apple Home), Samsung SmartThings, and Philips Hue.
Information from all devices and their attributes (entities) that the application sees can be used and controlled via automation or script using scheduling or subroutines (including preconfigured "blueprint"), e.g. for controlling lighting, climate, entertainment systems and smart home appliances.

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