From May 18th to the 21st, Microsoft is offering free online multiplayer to all Xbox Live players. This applies to those who have a Silver account for all multiplayer games that they already own. This offer is available on both Xbox One and Xbox 360.
Even more exciting is a limited time offer to unlock
for free, also from May 18 to 21! Download it
The free multiplayer and limited time offer begin May 18th and end on Sunday May 21st. Take advantage of the free opportunity!
Source: xbox one – Google News