2 App and content availability and experience may vary by region and device.

3 Cortana available in select markets at launch; experience may vary by region and device.

4 Features may vary by device. Microsoft account, Wi-Fi or data network connection required for some features; internet access fees apply.

The availability of Windows 10 Mobile as an upgrade for existing Windows Phone 8.1 devices will vary by device manufacturer, device model, country or region, mobile operator or service provider, hardware limitations, and other factors. 1.4 GB or greater download required. Wi-Fi internet connection is required to download and install the upgrade; internet access fees may apply. To check for compatibility and other important installation info, see Windows 10 Specifications page