What was the Xbox Series X's development codename?

The Xbox Series X was developed under the codename Project Scarlett.

Microsoft used Project Scarlett for its next-generation Xbox program before announcing the final names Xbox Series X and Xbox Series S. The project represented a new hardware generation after the Xbox One family and focused on faster loading, higher performance, and broader backward compatibility.

Xbox Series X launched on November 10, 2020, alongside Xbox Series S. The Series X became the more powerful model, while the Series S offered a smaller, less expensive design without a disc drive. Both systems use custom AMD hardware and share the same generation of Xbox software.

Project Scarlett should not be confused with Project Scorpio, the development codename for Xbox One X. Project Durango was associated with the original Xbox One, and Project Natal became Microsoft’s Kinect motion-sensing product.