[Update: Some users are reporting that Bethesda now has a pre-patched version of the game up on PS4 and Xbox making the download 51.6GB whereas the physical copies of the game still require installing from the disc and installing the game.]
Online only games have massive day one patches these days which in some cases (cough, cough Black Ops 4) require the entire game to be re-downloaded. While that seemed to be the case at first for Fallout 76, thankfully it’s not. However, the game will still require a substantial amount of downloading. Upon performing a disc-based install, those who bought the game on physical media will have 45GB of the required data already. After that, their PS4 will need to download 51.6GB worth of updates to the game. The resulting final file size will be 96.6GB, which means digital copy owners will need to download that amount to play.