You can play Halo Infinite right now. How to download the game's multiplayer mode

On Monday, Microsoft ended a celebration of the 20th anniversary of Xbox with a big surprise.

Halo Infinite, the upcoming action game launching in December for the Xbox Series X and S, is available to play early through a multiplayer beta launched Monday.

The announcement was made at the end of a livestream celebrating the 2001 launch of the original Xbox by Halo studio 343 Industries.

The beta is available on PC and Xbox. 

Halo Infinite has been described as a "spiritual reboot" of the original Halo game that launched with the first Xbox 20 years ago. The single-player campaign featuring the adventures of Master Chief launches on Dec. 8.

► Xbox 20th anniversary:  The 10 biggest moments for video game console

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Follow Brett Molina on Twitter: @brettmolina23.