Xbox Series S will run games designed for Xbox One in their 'One S' mode

[Windows Central]

One of the questions about the Xbox Series S has been answered.
The Xbox Series S is the affordable alternative to the next-gen Xbox Series X, designed to replace the current Xbox One consoles. The Xbox Series S is, over all, a superior system to that of the Xbox One X, but with some drawbacks in terms of RAM and raw GPU power. While games running on the next-gen GameCore OS environment should perform better than they would've done on the Xbox One X, games being built first for Xbox One will remain in their "Xbox One S" version on the Xbox Series X, and not take advantage of the 4K resolutions offered by Xbox One X titles.

Full story from the WindowsCentral blog...