: The user selects their country or region, and Windows displays a set of toll-free and toll numbers. Simultaneously, the screen presents a multi-digit Installation ID , which is unique to that specific hardware and license key combination.

Offline activation requires a valid product key. There is no legitimate way to activate Windows 10 without a key, online or offline. If you have no key, you can install Windows 10 but it will remain in an unactivated state with limited personalization features and a persistent watermark.

By following the phone activation route, you can ensure your system is fully functional and "Genuine" without ever having to plug in an Ethernet cable or connect to Wi-Fi.