The purpose of getting back the factory settings of a Google Nest Hub (f.k.a. Google Home Hub) is to amend common operating problems, usually due to misconfigurations made by the users. All pieces of information of users are taken away with this action, leaving the device just like new.
How to reset Google Nest Hub to its factory settings
One of the few things you can’t ask Google Nest Hub to do for you is to reset its factory settings. You will have to press the volume up and down buttons on the back of the device for 10 seconds. When you perform this action, a warning window will appear on the screen.
Note: It is not possible to reset the factory settings of Google Nest Hub using the Google Home app.