When Fallout 4 first released, developer Bethesda promised that they would be bringing mod support in the form of the Creation Kit as soon as possible. While modding have already been available since the launch on PC, this new kit allows players to customize the game in the same way that players have been doing with Skyrim for several years.
The Creation Kit essentially gives users the same tools that were used by the developers themselves to modify the game, giving them the opportunity to make significant changes. According to director Todd Howard, the aim is to release the update between the first two pieces of downloadable content. This gives it a likely release date of April, with the Xbox One version coming a month later and the PlayStation 4 edition a month after that.