You can disable the Office Online integration on your account. When you disable Office Online, you will no longer be able to preview and edit office documents in the Jottacloud web application.

Go to Connected apps settings to disable Office Online. Simply click the Disable button to disable the feature:

Note: if you disable the Office Online integration, we will not display previews of office documents shared with public links.

Office documents you preview or edit on Jottacloud will be sent to Microsoft Office Online for processing while you preview or edit them. To respect your privacy we have made the Office Online features optional. 

We will never send your documents to Microsoft Office Online servers without your consent.