How much RAM did the Xbox One have at launch?

The Xbox One had 8 GB of RAM at launch.

Microsoft equipped the original Xbox One with 8 GB of DDR3 system memory. The console also included 32 MB of embedded static RAM intended to help with graphics-related operations. This memory design differed from the Xbox 360, which used 512 MB of unified GDDR3 memory.

The Xbox One's 8 GB was shared by the operating system and games, so software could not use all of it directly. Microsoft reserved part of the memory for system functions, including the console's multitasking interface and entertainment features. Those features reflected the Xbox One's original positioning as an all-in-one television and gaming device.

The Xbox One X later increased the memory total to 12 GB of GDDR5, while the Xbox One S retained 8 GB of DDR3. Therefore, 8 GB describes the original Xbox One and Xbox One S family, but not every Xbox One-branded model.