X1 is the name of an operating system developed by Comcast for its line of next-generation video set-top boxes which also carry the X1 brand. The operating system offers access to Comcast’s live pay TV channels alongside third party streaming TV apps (Netflix, Amazon Prime Video, YouTube, etc.) and data services.
Comcast uses X1 for its own hardware and licenses the operating system to third party Internet and cable companies. X1 is also the operating system that powers Comcast’s streaming television box called Flex, which is offered to the company’s Internet-only customers.