Windows Phone 8.1 build 12075

8.10.12075.209.WPB_EXP_OFFICE.20130428-1100
	Build of Windows Phone 8.1
OS family	Windows NT
Version number	8.10
Build number	12075
Build revision	209
Architecture	ARM32
Build lab	WPB_EXP_OFFICE
Compiled on	2013-04-28
Base build
	6.3.9379.0.fbl_partner_mobile.130408-1200
About dialog

Windows Phone 8.1 build 12075 is the earliest known build of Windows Phone 8.1, which was uploaded to BetaArchive on 3 January 2020. It is based on Windows 8.1 build 9379 (fbl_partner_mobile).

New features and changes[edit | edit source]

This build of Windows Phone 8.1 incorporates many features rumored at the time, such as a new notification center, the ability to sort applications by most used, reworked versions of multiple existing system applications (indicated by a "z" in front of their names) and a preliminary version of Cortana, a digital assistant used to automate certain tasks such as calendar scheduling, reminders and searching for documents and on the Internet via the Bing search engine.

The version of Cortana included in this build can no longer be used as the respective Windows Live account authentication servers used by this build have since been taken offline.

Bugs[edit | edit source]

The NTFS driver is largely unstable in this build and may either wipe the eMMC, corrupt the respective file descriptor and/or (if the build bugchecks during the boot process) attempt to write garbage data to random disk sectors, including the EFI boot and board support package (BSP) partitions. An eMMC re-flash may be needed if these issues occur.