From Ubisoft: “To celebrate a new Hero joining the Hero ranks, and the arrival of the Outlanders, the Standard Edition of For Honor will be free this weekend. Warriors who wish to try For Honor will be able to do so this Thursday January 27th up to Monday January 31st. To ensure you are able to get in on the action once this “free weekend” begins, preload is available today, January 25th.”
Source: N4G PC For Honor Free Weekend across all platforms