Windows 10 Mobile Technical Preview: Update 1 (Build 10051)

Before you get further into this blog post and wonder why it may seem a little off, this is my first blog post about the Windows 10 builds for phones. There has only ever been one prior build for Windows 10 and phones, but I didn’t cover it as the Lumia 920 I have wasn’t in the supported devices list. I didn’t have any indication of when they might happen, so I skipped it. I only like doing a review for things I’ve actually laid my hands on.

The Lumia 920 I have had the latest updates applied to it from the developer preview program for 8.1 where application developers can get the latest updates directly from Microsoft rather than waiting for carriers to make it available to users. The version you see on my phone’s About screen may reflect a newer version as a result.


The build 9942 for Windows Phone devices (the first phone build) was fairly limited in it’s scope of supported devices given it’s initial size and the smaller memory capacities of the older, higher end phones. Sounds weird to say that the higher end phones have less memory than the lower end phones coming out, which shows how much Microsoft is focusing on emerging markets and the entry level side of the market compared to higher end iPhone and Galaxy users, but I digress.

If you didn’t have the Lumia 630, 635, 636, 638, 730, or 830, you were out of luck until now. The memory footprint of this update isn’t much smaller than before, but has a new feature to help it inch in the upgrade on these older devices. As explained on the first blog post over at Microsoft…

Some context on why we chose these and not higher end phones like the 930/Icon or 1520: We have a feature that will be coming soon called “partition stitching” which will allow us to adjust the OS partition dynamically to create room for the install process to be able to update the OS in-place. Until this comes in, we needed devices which were configured by mobile operators with sufficiently sized OS partitions to allow the in-place upgrade, and many of the bigger phones have very tight OS partitions.

Note that this doesn’t mean that Windows 10 will take more disk space than Windows Phone 8.1, it’s just a function of the upgrade process at this point. Once the partition stitching feature is completed, many more devices will be supported.

To recap what the first build included:

  • Full-size background image for Start screen
  • More Quick Actions in Action Center, taking the four programmable quick actions found in Windows Phone 8.1 up to three rows in Windows 10.
  • Interactive Notifications allows you to take action directly like dismissing an alarm, or seeing images for maps. For example, for text messages, when the toast pops, you can quickly reply inline via text or voice.
  • Significantly enhanced speech-to-text capability so you can talk to virtually any data field you choose. Your words show up as you speak them – and punctuation appears automatically.  This feature is smart enough to understand when to use ‘two’ – the number — instead of ‘too’ as in ‘also’.
  • More powerful Photos app that will show the aggregated set of all your local photos and all your OneDrive photos

Fast forward two months and here we are with the first build to incorporate this new feature for almost every Lumia phone out there under the Microsoft or Nokia branding. There are exceptions to this however, which would be the people who have the 930, 640XL, and the Icon. The reason these devices are excluded for now (but to be supported later) is due to a scaling issue where the UI appears too small to be usable and they have some work to do still in handling those special devices.

The new build for phones is 10051, and it’s currently only available for the Fast track for those that had one of the original six models. In comparison to the earlier build, a lot of areas of the phone build are in flight and it shows with the list of known issues listed below. Overall, if it’s a secondary phone you would be using with this update, do it. Otherwise I’d take Microsoft’s suggestion of not doing this on your primary phone, or at least not this build.

Interestingly enough, the build number given to us from Microsoft doesn’t match what the device reports, for whatever reason.


As for what is in the update:

  • An early version of Project Spartan is available in this flight. It uses the new rendering engine to give greater interoperability with the modern mobile web, and includes early versions of Reading View and Reading List. For now, it is not the default browser, and exists side-by-side with IE11.
  • Outlook Mail and Outlook Calendar are the new built-in mail and calendar universal apps for Windows 10. These new apps bring a fresh UI, with a toggle to freely move between your email and calendar without returning to the Start screen. Outlook Mail includes customizable Swipe Gestures, letting you swipe right or left to take actions like delete, flag, move or mark as read/unread. Also check out the new email authoring experience. Outlook Mail leverages the familiar capabilities of Word to create a richer email experience. You can do formatting tricks like inserting tables, adding pictures and using bullets and text. Outlook Mail and Outlook Calendar connects to Office 365, Exchange,, Gmail, Google Calendar, Yahoo!, IMAP, POP and other popular accounts.

    Note: To add or remove accounts in Outlook Mail and Outlook Calendar, you do so within these apps. The Email + accounts page has been removed from the Settings app.

  • You’ll see the new Phone and Messaging apps in this build. Give them a try and let Microsoft know what you think. The Messaging app has a new visual design. You can also easily upgrade from a messaging conversation to a voice call with one click of the phone icon in the new app bar.

    Note: If you are updating a phone from Build 9941 – please see below for a known issue regarding MMS that will require you to go use the Windows Phone Recovery Tool to roll back to Windows Phone 8.1 first and upgrade to this build in order to have MMS working on your phone.

  • The new universal People app has a new visual design but will continue to be the comprehensive list of all your contacts across services such as Exchange,, Gmail, Facebook, etc.
  • The first preview of the new universal Maps app on phone is now available. Maps offers you the features and tools you need to explore and navigate the world. This includes the best maps, aerial imagery, rich local search data, and voice guided navigation experiences from both Bing Maps and HERE maps, integrated together for the first time into a single app for Windows.
  • An updated app switcher can be access by pressing and holding the back button on the phone to see your recently used apps. Microsoft has added support for landscape when invoked from an app being viewed in landscape. For large phones like the Lumia 1520, they’ve introduced a new grid layout so you can be more efficient at switching between apps, and extended the length of recently used apps to 15.

Issues fixed in this build:

  • Updated the keyboard layout based on feedback to now include 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 like so…

wp_ss_20150411_0004  wp_ss_20150411_0005

  • Cortana icon resolution is fixed so it now scales with tile size.
  • 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.
  • 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.

Issues introduced in this build:

  • 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.

Things I found or experienced that weren’t in the list of known issues:

  • Attempting to take screenshots by doing Power + Volume Up, gives me a notification at the top that it “Can’t take screenshot”, but still manages to store the images.
  • Attempts to update installed applications fail with the 80073cf6 error code.

For the complete set of details, which most of it has been included here with marketing-speak removed, visit the Windows blog articles here for the first update or here for the second update. I’ll keep the phone edition of these builds going so long as my phone is supported and I can install it.