The 39.7GB file size is for the European version of the game, Guerrilla Games said, noting localized versions are closer to 37GB. By comparison, Infinity Ward recently announced that Call of Duty: Ghosts on PC will require 40GB of hard drive space.
Sony previously described Killzone: Shadow Fall as an "uber-file." The PS4 features a 500GB hard drive, though players can expand this, just like on the PlayStation 3.
Guerrilla Games technical director Michiel van der Leeuw told Eurogamer that the main reason for Killzone: Shadow Fall's near-40GB file size comes down to the art assets.
"The bulk of it is textures," he said. "I think we're probably a lot larger than the other cross-generation games, because we have no assets that have been made to a lower spec."
Van der Leeuw also called out the game's more open levels, compared to previous Killzone games. "The surface area, I'm just guessing here, must be five to 10 times bigger than Killzone 3 was," he said.
If 40GB sounds like a large file size, van der Leeuw explained that it could have been significantly bigger had the studio not reassessed its data management systems.
"I think at some point the disc image that we were generating was around 180 gigs," he said. "And if we would have put all the levels in, which we didn't, because then the disc image generator broke, it would have been around 290 gigs of data."
For those who purchase Killzone: Shadow Fall from the PlayStation Store next month, Sony's new PlayGo system--through which a portion of the game is playable before the full game finishes downloading--will allow gamers to get play more quickly, van der Leeuw said.
He explained that players with a "decent" Internet connection should be able to download an initial 7.5GB for the first level to start playing in a single evening. The full game should then be ready by the next morning. This could be improved further, van der Leeuw acknowledged.
"Realistically, I think a lot of people can do this... It's just that the initial chunk of 7.5GB is quite big. I think if we would have known exactly how everything would work... I think next time around we'll try to see if we can design something that doesn't jeopardize the game which will make it even friendlier," he said.
"But I think all things considered, this being launch and we've got like 2 minutes 44 from disc to the first level and no installs, I think it's already a massive improvement over previous generations," he added.
Killzone: Shadow Fall is a PS4 launch title, arriving in North America on 15 and Europe on November 29.