Bottom line: The restriction, of course, is due to speed. Microsoft wants optimized games to take full advantage of their new hardware, and specifically the 2.4 GB/s of raw throughput afforded by the custom NVMe SSD.

Three weeks out from the launch of Microsoft’s next-gen gaming platform, we are still learning new bits of information about the upcoming systems.

As you may know, the Xbox Series X comes equipped with a custom 1TB NVMe solid-state drive . In a screenshot of the storage devices menu courtesy of Tom’s Hardware , we see 781.0GB of available space (presumably after formatting, etc.). A video from YouTube user jackfrags, meanwhile, shows a bit more space at 802.0GB. I’m unsure why the two are different, maybe a different firmware version?

In any case, both sources reveal that games and apps on external drives must be stored on USB 3.0 devices with a capacity of at least 128GB. This restriction will eliminate the ability for some to repurpose older hard drives or lower-capacity flash drives.

Also worth noting is that storage drives must be formatted for the Xbox.

Tom’s Hardware further clarifies that games which are optimized for the Xbox Series X |S can be stored on external USB 3.0 drives but can only be played from the internal drive or on an “internal” expansion card . Titles that aren’t optimized, like original Xbox games, Xbox 360 titles and Xbox One games, can be installed and played from USB 3.0 devices.

Microsoft’s Xbox One Series X and Series S launch on November 10. They are priced at $499 and $299 and come with 1TB and 512GB of internal storage, respectively.