Yes, it is possible to play on multiple platforms (PlayStation®5, PlayStation®4, Xbox Series X|S, Windows, Mac, Steam) using the same Square Enix Account.

There are two methods to do this.

■If you wish to play on the same character across multiple platforms
Select the same Service Account for each platform when registering your registration code for the Windows, Mac, and Steam versions and when activating the PlayStation®5 and PlayStation®4 versions for the first time., you can use the same Square Enix Account to play on multiple platforms at the same time.
*Please take note that even if you register multiple versions of the game to a single Service Account, you will not be able to play simultaneously on all of those platforms.
*Also, please note that you cannot register the Windows and Steam versions to the same Service Account.

■If you wish to play on different characters for each platform
Select a different Service Account for each platform when registering your registration code for the Windows, Mac, and Steam versions and when activating the PlayStation®5 and PlayStation®4 versions for the first time., you can use the same Square Enix Account to play on multiple platforms at the same time.
*If you select a different Service Account during registration, then you will only be able to play the PlayStation®5 and PlayStation®4 versions of the game on the Service Account to which you registered the PlayStation®5 and PlayStation®4 versions, only the Windows version on the Service Account to which you registered the Windows version, and so on.

*You will be unable to change the selected Service Account later, so please use caution when registering your accounts.