Update: The public release build of Windows 10 Mobile is 10586.164 - the same build that has been available in the Windows Insider Slow/Preview Rings over the last two weeks.

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Windows Phone 8.1 users have been in desperation mode for several months now as they waited on the official release of Windows 10 Mobile for their handsets.

There have been build ups to possible release dates since last year but each slipped when the new mobile operating system was deemed not ready for public consumption.

The delays of the retail release also impacted brand new commercial devices like the Lumia 550, 650, 950 and 950 XL and other handsets that have been released for Windows 10 Mobile. Those devices basically hit the market with pre-release versions of Windows 10 Mobile running on them.

However, all of that waiting is now over, for the most part, and Windows Phone 8.1 users can now officially upgrade their eligible devices to Windows 10 Mobile without using the Windows Insider Program as a shortcut to the OS.

This article will provide you the details about the upgrade, how the process will work, resources that are available to assist you during the transition period and details about the specs those Windows Phone 8.1 devices must have to be eligible for the Windows 10 Mobile upgrade.

The most important starting point in this process is to make sure your Windows Phone 8.1 handset is running the Lumia Denim update. This is the baseline OS configuration necessary to get started so if your device was never eligible for Denim or your carrier did not release it for your handset then unfortunately this is the end of your Windows 10 Mobile upgrade process.

Once you are on Denim the next step to checking on your handsets status for Windows 10 Mobile is to download the Windows 10 Upgrade Advisor from the Windows Store.

Once installed just run the app and it will begin by checking your devices compatibility for Windows 10 Mobile. Your devices eligibility for Windows 10 Mobile will be based on a combination of variables including its current OS (Denim), firmware updates, the model is capable of running Windows 10 Mobile and the upgrade is available for your handset, region and operator. Minimum system specs are not the only criteria for getting the Windows 10 Upgrade on your device.

If the Windows 10 Upgrade Advisor determines that your handset is eligible for Windows 10 Mobile, you will have the option to enable the upgrade. Once the upgrade is located on the update server the phone will be ready to use the Phone Update in Settings to begin the process. At this point the upgrade sequence is very similar to any other past upgrade you have done for Windows Phone and can take up to an hour to complete depending on your connection speed and the amount of data on your phone that needs to be migrated.

If you have a handset and the upgrade is not yet ready for your device, then the upgrade advisor will let you know that and you will receive a notification on your phone when it becomes available in the future.

For those of you on handsets that are not eligible for the Windows 10 upgrade for whatever reason, the upgrade advisor will notify you of that fact but this will also mean the end of the road for you when it comes to Windows 10 Mobile.

If your device is eligible for Windows 10 Mobile and you are not ready to upgrade, something I doubt will be an issue for most users after the long wait, you can postpone grabbing Windows 10 Mobile by not checking the Enable Windows 10 upgrade box in the upgrade advisor app. Once you are ready for the upgrade just re-run the upgrade advisor app to get started once again.

The upgrade advisor will also let you know if space has to be freed up to perform the upgrade and give you an opportunity to clean things up and move items to an SD card as necessary. Once that space is sorted out you will be able to proceed with the upgrade.

Some other resources and items you should be aware of include:

  • These devices are eligible for the upgrade: Lumia 1520, 930, 640, 640XL, 730, 735, 830, 532, 535, 540, 635 1GB, 636 1GB, 638 1GB, 430, 435, BLU Win HD w510u, BLU Win HD LTE x150q, MCJ Madosma Q501.
  • Be sure your phone has at least a 50% battery charge. So many times I have had to wait to install a new update because of not being charged up!
  • After upgrading be sure to head into the Windows Store and check for app updates to insure you have the latest available versions.
  • If you are a Windows Insider and running Windows 10 Mobile on a device that previously had Windows Phone 8.1 on it and it is eligible for the uprgade, you will need to use the Windows Device Recovery Tool (WDRT) and reinstall the original Windows Phone 8.1 OS. After it is installed and running Denim you can download and use the Windows 10 Upgrade Advisor to get started.
  • Microsoft’s Answers Community Forums will be available to discuss your upgrade and get help if needed.
  • If you have never run Windows 10 Mobile through the Windows Insider Program, then you may be interested in learning what all is new in the updated OS to get started.
  • Check out the Windows 10 Mobile Hardware Specs page to see where your device fits in.
  • Microsoft Windows 10 Mobile information website including FAQ and other support links.
  • Windows 10 Mobile Update Error Codes
  • You can even reach out to Microsoft through their various social media accounts for assistance. Those include @MicrosoftHelps, @LumiaHelp, @Windows and @WindowsInsider.

If your device is not going to ever be eligible for the public Windows 10 Mobile release it may still be possible for you to grab the OS through the Windows Insider program.

Track Windows 10 Insider Builds for PC and Mobile Devices

Like any big operating system release of this magnitude patience is key because it takes time from the announcement of the upgrades availability until it is staged for all locales and there will be bumps along the road.

If you have any questions about the process, feel free to use the above resources I mentioned or ask a question in the comments. We will do everything possible to provide whatever assistance is possible.

Good Luck with your upgrade and let us know how it goes.

But, wait...there's probably more so be sure to follow me on Twitter and Google+.