A little over eighteen months ago, Microsoft announced that they would be making Xbox 360 games playable on the Xbox One. This technical feat was impressive, taking into account that the two consoles have vastly different processor architectures and that Microsoft made these games available to gamers at no extra charge, if they already owned the game digitally or physically.
What type of Witchcraft is this?
No witchcraft is involved, only very clever engineering. The Xbox 360 has an IBM PowerPC CPU and the Xbox One has an AMD x64 CPU, meaning they have a different number of processors, those different processors work at different speeds and essentially speak completely different languages to understand and issue commands.
The Xbox Team have used their extensive knowledge to build a translator for those commands and the different speeds at which the CPU processors work. This translator is called an Emulator and is a program that asks itself "If this command was given to an Xbox 360, what would it do to handle it?" and provides that command in a way that the Xbox One understands.
There are many different kinds of Video Game emulators available online, most developed by hobbyists to keep their old video game library alive. The developers of these emulators have spent hours breaking down at the machine code, debugging level what exactly happens within the processor of a console at a certain time when something happens and then make an educated guess of what should happen in a modern CPU.
The engineers at Microsoft had a slight advantage in that they knew from the original designs of the Xbox 360 what should be happening. However, to get an emulator running and to get an emulator running well are two very different things.
What types of Games are available?
While some gamers may have dabbled with emulators on the internet before, often they are ok but don't run all games well or have unexpected behaviour in some places because the developers of the emulator had not predicted for certain behaviour.
Where Xbox has excelled is to effectively load a full Xbox 360, including the OS from the Xbox 360, each time you run a Backwards Compatible game. Your Xbox 360 game does not know anything about the Xbox One and thinks that it is running on Xbox 360 hardware.
This has made it possible to have full games, rather than only the smaller 'Arcade' games work reliably to work on the newer console.
Good news came from Head of Xbox, Phil Spencer, this week that he plans for Backwards Compatibility to be a key feature of Xbox for years to come. Microsoft's as yet unnamed console, Project Scorpio will be able to play all Xbox One games and hundreds of Xbox 360 titles when it launches around Christmas / Thanksgiving this year.
As of 1. February 2017, here is the list of Xbox 360 games that you can play on your xbox.
Full Games / Games on Demand
Alice: Madness Returns
Assassin’s Creed II
Banjo-Kazooie: Nuts & Bolts
Battlefield 3 (Disc Only)
Battlefield: Bad Co. 2
Bound by Flame
Bully Scholarship Ed.
Call of Duty 2
Call of Duty 3
Call of Duty: Black Ops
Call of Duty: World at War
CLANNAD (Only available in Japan)
Condemned: Criminal Origins
de Blob 2
DEUS EX: HUMAN REVOLUTION
DOOM 3 BFG Edition (only available on disc)
Dragon Age: Origins
Dungeon Siege III
Escape Dead Island
Fallout: New Vegas
Gears of War
Gears of War 2
Gears of War 3
Gears of War: Judgment
Injustice: Gods Among Us (+ disc only Ultimate Edition)
Jurassic Park: The Game
Just Cause 2
Kameo: Elements of Power
Kane & Lynch 2
Killer Is Dead
Left 4 Dead
Left 4 Dead 2
LEGO Pirates of the Caribbean: The Video Game
LEGO Star Wars: The Complete Saga
Mass Effect 2 (disc only)
Mass Effect 3 (disc only)
Midway Arcade Origins
MX vs. ATV Reflex
Of Orcs and Men (not available in all regions)
OFP: Red River (disc only, except Japan)
Operation Flashpoint: Dragon Rising
Perfect Dark Zero
Pure (disc only)
RAGE (disc only)
Red Dead Redemption
Saints Row IV
Shadows of the Damned
Silent Hill: Downpour
Sonic & All-Stars Racing Transformed
South Park: The Stick of Truth
Star Wars: The Force Unleashed
Star Wars: The Force Unleashed II
Supreme Commander 2
Tekken Tag Tournament 2
The Orange Box
The Witcher 2: Assassins of Kings
Tom Clancy’s Rainbow Six Vegas
Tom Clancy’s Rainbow Six Vegas 2
Tour de France 2011 (not available in all regions)