Lumia Phones get updated Lumia
Windows 10 Technical Preview for phones available Microsoft

Microsoft has released the new Windows 10 Technical Preview for phones with build 10051 to the Fast ring.

Available across a larger set of Lumia phones, the new build does not support Lumia 930, Lumia Icon and 640 XL, due to an issue with scaling, which makes the UI too small to be used. The company confirmed that it is working on adding code to support scaling for the aforementioned devices.

Supported Lumia devices

Lumia 1020, Lumia 1320, Lumia 1520, Lumia 520, Lumia 525, Lumia 526, Lumia 530 (Dual-SIM), Lumia 535, Lumia 620, Lumia 625, Lumia 630 (Dual SIM), Lumia 635, Lumia 636, Lumia 638, Lumia 720, Lumia 730 (Dual SIM), Lumia 735, Lumia 810, Lumia 820, Lumia 822, Lumia 830, Lumia 920, Lumia 925, Lumia 928, Lumia 430, Lumia 435, Lumia 435 (Dual SIM), Lumia 435 Dual SIM DTV, Lumia 532 (Dual SIM), Lumia 640 Dual SIM and Lumia 535 Dual SIM

You can get the latest build via the Windows Insider Program. Once your device is ready on Windows 10 Technical Preview, just go to Settings>> Update & recovery >>Phone update>> Check for the updates.

What is new

Project Spartan: An early build of Project Spartan is available, using the new rendering engine to offer interoperability with the modern mobile web, while including early versions of Reading View and Reading List.

New mail and calendar apps: Outlook Mail and Outlook Calendar are the new built-in universal apps for Windows 10, with a fresh UI and toggle to switch between mail and calendar without returning to the Start screen.

New Phone and Messaging apps: You can enjoy the new Phone and Messaging app, with a more current visual design in the build.

New People app: There is a new People app having a revamped visual design that will have the list of all your contacts across services such as Exchange, Outlook, Gmail and Facebook.

New Maps app: The first preview of the universal Maps app is now available.

Updated App Switcher: The app switcher adds support for landscape when invoked from an app being viewed in landscape. A new grid layout that allows switching between apps has been introduced for large screen phones like the Lumia 1520.


  • We've updated the keyboard layout based on your feedback. The keyboard layout now has period, comma and emoji keys on first page of keyboard. Language switching is enabled by press-and-hold on the &123 key. There is also an option to replace the emoji key with the language switching key.
  • We've fixed the Cortana icon resolution so it now scales with tile size.
  • We've fixed the issue where the Photos app would fail to launch periodically when attempting to add a photo attachment to an email, OneNote or Facebook item.
  • We've fixed the issue where the Microsoft Band wouldn't sync with your phone after upgrading to Windows 10.
  • The Photos app's tile will now pick up the phone's theme color before it's launched and then start showing pictures from your collection including OneDrive in the Live tile.

Known issues

  • There might be situations in which auto-upload of your Camera Roll to OneDrive may not be working. Please be sure to back up your photos especially if you need to use the Windows Phone Recovery Tool to go back to Windows Phone 8.1.
  • The Office Hub has been removed from this build. You won't be able to open Word, Excel, PowerPoint or OneNote files in this build. Preview versions of the universal Office apps will be available in the coming weeks.
  • All Bluetooth-based interactions with Cortana are not working in this build because we're reworking how Cortana interacts with Bluetooth. This includes dictating and reading text messages, initiating searches and chit-chat, and all system-level control (such as playing music, launching applications, or navigating settings.
  • After upgrade, some apps that have been installed onto a SD memory card will fail to launch. To fix this, uninstall and reinstall the apps.
  • About 1% of the time, incoming phone calls may not play a ringing sound.
  • Call + SMS filtering will not work after upgrade.
  • For people upgrading their phone from Build 9941, there is a bug in which your phone's MMS settings will be lost after upgrade. The new Messaging app doesn't yet have the ability to re-enter these settings. You will need to use the Windows Phone Recovery Tool to go back to Windows Phone 8.1 and then upgrade to this build to get MMS working again.
  • Also for people upgrading their phone from Build 9941, the tiles on your Start screen for the Camera and Photos apps may be missing or corrupt. You will have to unpin any corrupt tiles and re-pin the apps to your Start screen.
  • On some phones, due to a scaling bug the dismiss button won't be visible when an alarm is triggered. To stop your phone from "alarming "just touch the arrow and swipe up on the notification and off the screen to end the alarm.
  • On phones with 512MB of memory, apps can randomly crash due to an issue with memory management.
  • Flight mode cannot be enabled.
  • Data connections can't be disabled.
  • You may need to re-pin the Phone app after upgrade.
  • The Insider Hub is now included on Phone but may fail to launch on some phones.

Head over to the Microsoft Windows Blog to know more about Windows 10 preview for phones build 10051.