A Microsoft Office 365 product key is a unique 25-character alphanumeric code used to validate your ownership of the software 1.2.25 . It acts as the digital "key" that unlocks the full functionality of the apps 1.2.25. XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
Use a free tool like (from NirSoft) to view installed Office keys — but note: modern Office 365 often shows a generic key, not your actual license. office 360 product key
