According to 343 Industries, The achievement support “will differ according to the title because any support that specifically requires reconciliation and challenges will not be obtainable.” The culprits who will lose achievement support are Halo: Reach, Halo 4, and Halo 3. The chart above shows that accomplishments for Halo 3: ODST, Halo Wars and Halo: Spartan Assault should remain unaffected, while Achievements for Halo: Combat Evolved Anniversary can All to be unlocked. To be on the safe side, it will be helpful to work through all of Halo-branded Xbox 360 Achievements online should this happen.
All of these games have also been deleted from the Microsoft Store, so if you haven’t played these titles and want to start working with their achievement lists, you will need to find physical copies of each game. As a side note, Halo: Spartan Assault (Xbox 360) includes One achievement partially discontinued / unobtainable It is not available physically.
343 Industries says online services will be closed sometime after December 18, 2021. You have a year to unlock any of the achievements from these games before they’re discontinued.
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