for on-line quickbook, where is the data file saved?

Afaik, Intuit is using AWS to host QBO.

Hello waikei0612. I appreciate you connecting with us here. QuickBooks makes it easy to keep track of your data while you get ahead with your work using the powerful features offered in the program. Your data is safely stored on servers that are across Canada and the US. Feel free to ask other questions, I'm here to help.