.HOI4 File

The hoi4 file extension is likely only associated with Hearts of Iron IV, the latest installment of the WW2 grand strategy game series from Paradox Interactive.

The hoi4 file presents saved game position.

How to open:

When placed in the default Save Game folder (In documents), you will be able to load the saved position.

How to convert:

There is no way how you can convert .hoi4 saves to anything else.