User space refers to all of the code in an operating system that lives outside of the kernel. Most Unix-like operating systems (including Linux) come pre-packaged with all kinds of utilities, programming languages, and graphical tools – these are user space applications. We often refer to this as “userland.”

What is the difference between kernel and user space?

Kernel space is strictly reserved for running a privileged operating system kernel, kernel extensions, and most device drivers. In contrast, user space is the memory area where application software and some drivers execute.

What is user address space?

The virtual address space for a user-mode process is called user space. In 32-bit Windows, the total available virtual address space is 2^32 bytes (4 gigabytes). Usually the lower 2 gigabytes are used for user space, and the upper 2 gigabytes are used for system space.