Does user need to sign in to edit document in Office Online Server through WOPI?

Question

We have a successful integration between our product and Office Online Server through WOPI. In the past, there was a behavior that user needs to sign-in to Office365 before editing documents in the Office Online Server through WOPI. But, nowadays it seems users do not need to sign-in to Office365 anymore, even in private mode (incognito).

1. Is this a new flow that user does not need to sign in anymore when editing documents in Office Online through WOPI?
2. When editing documents in Office Online, which account in Office365 or license is being used?
3. In which Office365 account does the document belong to?

Answer 1

1. Sign-in is not required for editing or viewing documents via WOPI host
2. For editing documents via WOPI host it is supposed that users have a proper license (it is not checked automatically).
3. The document does not necessary belong to an Office365 account.