No, you will not be able to play Diablo 4 without an active internet connection. This was confirmed by Blizzard Entertainment , when during BlizzCon it was asked whether it is legitimate to expect full support for an offline mode.
Angela Del Priore, lead designer of the game, explained that “we will not support an offline mode. But, as we have already said, nothing in Diablo 4 will force you to make groups with someone. You can also play dungeons completely by yourself, or play in private. The quest areas of the campaign will remain private. “
Blizzard has also confirmed that the above is valid for all platforms – then PC, PlayStation 4 and Xbox One. For all the further details on the already long-awaited next appointment with the Diablo saga, we refer you to our card.