Azure AD Join: What happens behind the scenes?

In a previous post we discussed about the three ways to setup Windows 10 devices for work with Azure AD. I later covered in detail how Windows 10 domain joined devices are registered in Azure AD. In this post I want to provide some insight about what happens behind the scenes when users join devices to Azure AD (Azure AD Join).

Users can join devices to Azure AD in two ways: 1) through the out-of-box experience (OOBE) the very first time a device is configured (or after a device reset to factory settings) or 2) through Settings after configuring the device with a Microsoft account (e.g. Hotmail) or local account.

In both cases what happens behind the scenes is fundamentally the same:

1. User chooses to join device to Azure AD.
2. User authenticates and provides an MFA proof (if configured).
3. User accepts terms from MDM system (if applicable).
4. Device registers with…