Windows 10 uses less storage space on some devices because Microsoft compresses system files. That saves up to 2.6 gigabytes of storage space. Also, Windows 10 no longer has a recovery image, which saves 4 to 12 gigabytes.
Compressing system files can save 1.5 gigabytes on 32-bit devices and even 2.6 gigabytes on 64-bit devices. Microsoft reports this on its own Windows blog. Not all devices with Windows 10 will be able to use compression: a computer must have sufficient internal memory and a processor that is fast enough to be able to decompress files quickly enough.
Devices running an earlier Windows version will automatically get the compression feature when they update to Windows 10, provided the device meets the system requirements. New devices that ship with Windows 10 will use the compression if the manufacturer enables it.
In addition, Windows 10 will no longer provide a recovery image, which also saves 4 to 12 gigabytes. Many manufacturers now include that recovery image so that users can reinstall Windows. Instead, Windows 10 will be able to repair itself, which Windows 8 already can. Users can make their own recovery disk, which will also back up installed software. That drive is for times when the system is so badly damaged that the recovery process no longer works. Thanks to these measures, more storage space is available to users on systems as standard.