Compatibility specs...?

I understand this product is compatible with both Mac and Windows. My question is: If I have a Mac and my boyfriend has a PC, are we both able to use this product as a backup hard drive at the same time? Or is only made to be compatible with one or the other?

G-Technology 4TB G-DRIVE Desktop Hard Drive - USB 3.0

G-Technology 4TB G-DRIVE Desktop Hard Drive - USB 3.0

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