Storage space isn’t an issue until it runs out. Then it’s time to save or expand space. What many users don’t know: Windows has built-in hidden functions that can be used to easily shrink an installed system and thus save a few GB of space on the hard drive or SSD.
Windows is not a particularly bloated system, but version 10 occupies around 15 GB of storage space in the 64-bit version, according to Microsoft. But that alone is of course not enough in practice: there is also space for updates, system restore points, temporary files and more.
Of course, no additional installed programs are taken into account here. You can view the space required by your installation in Windows “Memory Usage”. In the “System and reserved” area, for example, 26.7 GB appear on a test machine in the editorial office, a realistic value for a typical Windows.
Built-in compression CompactOS
When the hard drive or SSD is full, nothing works. With the built-in CompactOS compression, you can quickly free up a few GB of space under Windows.
The principle: Windows compresses the system files and practically shrinks itself. This also happens automatically when Windows recognizes that the free storage space is running low.
Start a command line with admin rights. With the command compact /compactos:query query the current status. Windows may state here that there is no benefit from compression on the existing system. Then it is advisable to keep your hands off the compression.
Shrink Windows installation
To compress Windows 10 system files, use the command compact /compactos:always. After a few minutes, the tool will show how successful it was at compressing.
In our test run on Windows 11, we were able to save around 4.5 GB of space in just a few minutes. Microsoft itself states that of the around 15 GB that Windows 10 should occupy, you can save 3.7 GB with the command.
It’s not particularly much that you get out of compressing Windows binaries. So the function is more of an emergency nail if your disk fills up and you otherwise hit a wall on a system. In such emergencies, Windows also activates the compression itself.
undo reduction
Note that CompactOS saves space but costs performance because the system files always have to be decompressed first. So test whether the compression on your system is a help or slows you down too much.
If the disadvantages outweigh the disadvantages, you can use the command compact /compactos:never undo the compression.
But the Compact command used can do even more: You can also use it to compress folders. There is even a small tool with a graphical interface that you can use for this purpose.