Yes, Greenback is compatible with the QuickBooks Online (and QuickBooks Online Accountant) Desktop App made for Mac and Windows computers. You can launch Greenback through their app or through a standard web browser at https://www.greenback.com/auth/signin. (While it is possible to use QuickBooks Online and the QuickBooks Windows or Mac app at the same time, please note that their app does not share data with any QuickBooks Desktop company files since they are different products.)