The changed login requirement for Microsoft 365 vs Office 2021/2019 makes sense because the software licence is different for each. Sign in difference Office 2021 vs Microsoft 365 They may have other, unstated reasons too. Microsoft’s position is that with a sign-in you can access any OneDrive files directly from the Office apps. If Office 2021 doesn’t need a Microsoft account sign in, why is it there at all? However, after activation, the MS account isn’t necessary for ongoing use. Software activation, after installation, does require a Microsoft account. Free OneDrive has 5GB ‘only’ but that’s a lot of Office documents! Activation Office 2021 doesn’t include any extra OneDrive storage. The OneDrive app will need a Microsoft account login, obviously. After you’ve changed the documents, they’ll be copied back to OneDrive. Office 2021 can open those locally stored documents. The OneDrive app for Windows and Mac lets you sync your online storage with local folders. While it’s convenient to access OneDrive saved documents via the Office File | Open dialogs there is an alternative. Microsoft encouraged customers to sign into a Microsoft account (with the same warning message) but Microsoft account sign-in is not necessary. Here’s Excel 2021 open with a worksheet and Word 2021 also open, ready to make a new document or work on an existing one. Editing files in Word, Excel or PowerPoint is quite possible without signing in. The second paragraph is wrong according to our tests. See Two ways to open a OneDrive document in Microsoft Office However, if you’re using the OneDrive app to sync files then you’ll still be able to work with OneDrive documents be opening them in the local OneDrive folder. Any cloud stored files should be saved (to the cloud or a local drive) before logging out. When you’re ready to edit files on this device, sign in to Office again. To complete the process, close all Office apps. Save any Office files that sync to the cloud (such as OneDrive) before you sign out.

Signing out will remove your account from this and other Office apps. It says more about Microsoft’s desire to have all their customer logged into their system.

How to activate microsoft office on mac