As Windows 10 Mobile heads into the final stretch in its development, its scheduling and update limitations are starting to become clearer. One of those limitations effects Windows Phones with less than 8GB of dedicated internal storage. Phones with 4GB of internal storage are evidently going to sit out the upgrade.

The news comes via the German version of the Windows 10 Mobile site. Under the section detailing that current phones will get the update it notably mentions "8GB internal memory required." Interestingly, the U.S. version of the same page does not mention this necessity. However, it does list devices with only 8GB of internal storage.

Up until now, it has been speculated that phones with 4GB would not get Windows 10 Mobile as they are currently excluded from the Insider preview. However, now it looks like this situation will remain going into the official release too.

Of course, like all things, some perspective is needed. Specifically, there are very few recent Windows Phone with only 4GB of storage. Indeed, going back to our forums, it was pointed out a few times that devices with 4GB of memory still could not use the Windows Insider program. Currently, ineligible phones include:

  • Alcatel One Touch Pixi 3 Series Handsets (Windows Models)
  • Nokia Lumia 530
  • HTC 8S
  • Blu Win JR and JR LTE
  • Yezz Billy 4
  • Karbonn Titanium Wind W4
  • Kazam Thunder 340W, Thunder 450 and 450WL

Indeed, earlier this month Kazam reportedly took their name off of the Windows 10 Mobile upgrade list. This decision despite the fact that the 450 series does have 8GB of storage.

Except for the poorly-received Lumia 530, the rest are reference designed phones that represent a tiny minority of devices, according to the latest AdDuplex numbers.

The reason for excluding phones with 4GB of storage comes down to the simple 'not enough room' problem. Windows 10 Mobile is about 1GB bigger than Windows Phone 8.1 due to many shared components between it and its desktop sibling. Users trying to force the upgrade will just run out of room due to not having enough free space.

Microsoft Germany has even posted the storage requirements for Windows 10 Mobile:

Microsoft seems to have anticipated this situation as these recent phones are still slated for Windows 10 Mobile, first announced at the end of July.

Official eligible phones for Windows 10 Mobile upgrade

  • Lumia 430
  • Lumia 435
  • Lumia 532
  • Lumia 535
  • Lumia 540
  • Lumia 640
  • Lumia 640 XL
  • Lumia 735
  • Lumia 830
  • Lumia 930

The Windows 10 Mobile update is expected to occur in waves like previous updates starting possibly in October. The devices not listed above still have access to the Windows Insider program to utilize Windows 10 Mobile. Indeed, much like the desktop version of Windows 10, those on the Insider program are likely to get the "RTM" version of the OS well ahead of any carrier updates.

At this time, it is not clear if the officially updated devices are also slated to get an accompanying firmware update.

Although it is unfortunate that phones with 4GB of memory cannot get Windows 10 Mobile it appears to impact a small minority of users. Additionally, this is not news either as so far those devices have been ineligible for the Preview.

Will your phone not be eligible for the update? Share your thoughts in comments.

Source: Microsoft (Germany), Microsoft (U.S.); via BetaNews