Windows 10 Storage Requirements Are Variable

Users are often confused by why the OS uses so much storage on a local device. Other than the files in the OS directory (generally C:Windows), several other components require space on a local storage device. In this illustration, the top bar represents a hard drive in a device running Windows 10. Here, approximately one gigabyte of storage is consumed even before the OS is installed for data needed by the OEM and the extensible firmware of the device (the EFI and OEM partitions).

The middle bar represents the partition of the hard drive where the OS is installed (generally the user’s C: drive). This is the space consumed by the user’s documents (docs), applications (apps), temporary files (temp), system and reserved files, and other storage. In this illustration most of the space is still available for the OS or the user’s files. Should the amount of available free space become too low, the OS can fail, particularly during space intensive operations such as installing a new feature or cumulative quality update.