As you may know, Microsoft has announced some improvements on OneDrive for Business – such as a new synchronization client and a new web UI (see https://blog.onedrive.com/meet-the-new-onedrive-for-business/)
If you have enabled First Preview for your tenant (all organization or selected users) you may already have the new web UI available as per below
Each user with the new interface has the ability to switch back to the previous web UI using the Return to classic OneDrive link shown in the bottom left
However, if you – as administrator – want to disable the new UI for ALL users, you can do it from the SharePoint Administration center
Just go to the Settings section and locate the OneDrive for Business experience which should be at the top and switch the setting from New experience to Classic Experience
