Client/Server Runtime Subsystem

<p>The Client/Server Runtime Subsystem, or csrss.exe, is a component of the <a href="/facts/Windows_NT/EtccWvxQ">Windows NT</a> family of <a href="/facts/Operating_system/8XTuvMh2">operating systems</a> that provides the <a href="/facts/User_space/0yIzMY8t">user mode</a> side of the <a href="/facts/Windows_API/RRw4RtTu">Win32 subsystem</a>. In modern versions of Windows, it is primarily involved with process and thread management, <a href="/facts/Win32_console/p8vz2Cdk">console window</a> handling, <a href="/facts/Side-by-side_assembly/vBhren6q">side-by-side assembly</a> loading and the shutdown process. Historically, it had also been responsible for window management and graphics rendering, however, these operations have been moved to <a href="/facts/Kernel_mode/27y4kjHs">kernel mode</a> starting with <a href="/facts/Windows_NT_4.0/EcKYxrkx">Windows NT 4.0</a> to improve performance.
</p><p>CSRSS instances are marked as critical processes, meaning that terminating one will <a href="/facts/Blue_screen_of_death/f7LFeRBa">crash</a> the system. Built-in process management tools in most Windows versions will also refuse to kill instances of CSRSS. Under normal operation, there is a CSRSS instance for each session (two in <a href="/facts/Windows_Vista/IASEUCTB">Windows Vista</a> and newer, one in earlier versions, both assuming there are no active <a href="/facts/Remote_Desktop_Protocol/A5e9ILdI">RDP</a> connections which spawn extra sessions).
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Client/Server Runtime Subsystem open-in-new

Client/Server Runtime Subsystem