Matter (formerly CHIP, Connected Home over IP) is a residential IoT interoperability standard maintained by the CSA (Connectivity Standards Alliance), letting a single device be controlled simultaneously by Apple Home, Google Home, Amazon Alexa and Samsung SmartThings.

Matter's founding characteristics are multi-ecosystem operation (one device exposed to multiple administrators in parallel), an open standard governance with the CSA plus Apple, Google, Amazon and Samsung as principal contributors, IP-only transport over Wi-Fi, Thread or Ethernet, and an open-source SDK hosted at github.com/project-chip. Spec 1.0 was published in October 2022 and the cadence has since reached 1.4 (October 2024). Matter standardises what Apple HomeKit, Google Home and Alexa historically did with separate proprietary protocols.

Remember the parentage: CSA is the standards body, project-chip is the GitHub home of the SDK, and CHIP is the legacy name you still see in source code and older marketing material.