BridgeOS

bridgeOS is an embedded operating system created and developed by Apple Inc. for use exclusively with its hardware. bridgeOS runs on the T series Apple silicon processors^[1][2][3][4] and operates devices such as the OLED touchscreen strip called the "Touch Bar",^[5] TouchID fingerprint sensor, SSD encryption, and cooling fans.^[6]

bridgeOS
Developer	Apple Inc.
Written in	C C++ Objective-C Swift assembly language
OS family	Unix-like, iOS
Working state	Current
Source model	Closed, with open-source components
Initial release	October 27, 2016; 8 years ago (2016-10-27)
Update method	FOTA (via Mac running macOS)
Platforms	T series (2016 MacBook Pro and later)
License	Proprietary software except for open-source components
Support status
Supported

At boot time, the bootloader executes the bridgeOS kernel, then the bridgeOS kernel passes off to the UEFI firmware.^[7]

bridgeOS is based on Apple's watchOS.^[8]