Microsoft has announced that it is formalising the arrangement whereby Windows 10 inexplicably swipes a chunk of disk space for its own purposes in the form of Reserved Storage.

The theory goes like this – temporary files get generated all the time in Windows, either by the OS or apps running on the thing. As a user's disk fills up, things start getting sticky as space for this flighty data becomes short and reliability suffers.

Microsoft has tried a few ways over the years to help users manage disk space – Windows will start to whinge as disks reach capacity and built-in tools exist to clear unwanted files. The latest, Storage Sense, will quietly "dehydrate" OneDrive files to free up space.

It appears that such tools aren't enough.

In 2019, Microsoft is throwing in the towel. New installs of Windows 10 1903 (currently with Windows Insiders in the form of 19H1 and expected in the hands of users sometime in April) will feature "Reserved Storage".

Reserved Storage effectively blocks out a chunk of disk for temporary files generated by the likes of apps or OS updates. The gang at Redmond reckons that 7GB of sacrificial space will be a good starting point, but the total might vary over time. You can also shrink the reservation, but never remove it from the OS entirely.

Never mind the Reserved Storage, how has Microsoft got system files down to 5.5GB? Pic: Microsoft

Users can then cheerfully use their PCs without worrying about their free space suddenly disappearing as a colossal Windows update gets silently downloaded in the background. That space has been pre-nabbed ready for all those temporary(ish) files.

Unless, of course, the Reserved Storage fills up. In which case it will be business as normal as Windows temporarily consumes space outside the reservation, thus somewhat defeating the point of the thing.

Slightly ominously, Microsoft also said: "We may adjust the size of reserved storage in the future based on diagnostic data or feedback."

Windows Insiders will be able to experience the functionality for themselves if they are willing to fiddle with a Registry setting before the next build drops.

So, if you're buying a PC in 2019 and considering disk space, remember that as well as all the recovery and system partitions which will adorn your system, Windows 10 will want its own piece of the action as well. ®